Fix an Issue with new Resource Desginer Assembly

[dellis1972]

Context mono/SkiaSharp#2444.

So while investigating the issue above we found there is an issue with the new Resource Designer Assembly implementation. The problem in the issue linked was that the SkiaSharp.Views Nuget package was not shipping the .aar file for its net8.0-android platform. As a result the ignorePixelScaling field in the ShiaSharp.Views assembly was not found in the new Resource Designer Assembly. This results in the field NOT being changed to use the Resource Designer Assembly Property (because it does not exist). It is this which results in the runtime error

System.BadImageFormatException: 'Invalid field token 0x040000a1'

We decided that instead of ignoring missing resource fields, we should error out. This PR includes an update to the FixLegacyResourceDesignerStep which will throw and exception if we cannot find the required property to match a field. The new error will be the following for Debug builds

error XALNS7009: System.InvalidOperationException: Could not find an 'AndroidResource' for 'Styleable/SKCanvasView'. To Fix this issue add the required 'AndroidResource' item to your project.

or for Release builds

Fatal error in IL Linker (TaskId:87)
                     Unhandled exception. System.InvalidOperationException: Could not find an 'AndroidResource' for 'Styleable/SKCanvasView'. To Fix this issue add the required 'AndroidResource' item to your project. (TaskId:87)
                        at MonoDroid.Tuner.FixLegacyResourceDesignerStep.FixBody(MethodBody body, TypeDefinition designer) in xamarin-android/src/Xamarin.Android.Build.Tasks/Linker/MonoDroid.Tuner/FixLegacyResourceDesignerStep.cs:line 151 (TaskId:87)
                        at MonoDroid.Tuner.LinkDesignerBase.FixType(TypeDefinition type, TypeDefinition localDesigner) in xamarin-android/src/Xamarin.Android.Build.Tasks/Linker/MonoDroid.Tuner/LinkDesignerBase.cs:line 116 (TaskId:87)
                        at MonoDroid.Tuner.LinkDesignerBase.FixupAssemblyTypes(AssemblyDefinition assembly, TypeDefinition designer) in xamarin-android/src/Xamarin.Android.Build.Tasks/Linker/MonoDroid.Tuner/LinkDesignerBase.cs:line 185 (TaskId:87)
                        at MonoDroid.Tuner.FixLegacyResourceDesignerStep.ProcessAssemblyDesigner(AssemblyDefinition assembly) in xamarin-android/src/Xamarin.Android.Build.Tasks/Linker/MonoDroid.Tuner/FixLegacyResourceDesignerStep.cs:line 99 (TaskId:87)
                        at MonoDroid.Tuner.LinkDesignerBase.ProcessAssembly(AssemblyDefinition assembly) in xamarin-android/src/Xamarin.Android.Build.Tasks/Linker/MonoDroid.Tuner/LinkDesignerBase.cs:line 198 (TaskId:87)
                        at Mono.Linker.Steps.BaseStep.Process(LinkContext context) (TaskId:87)
                        at Mono.Linker.Pipeline.ProcessStep(LinkContext context, IStep step) (TaskId:87)
                        at Mono.Linker.Pipeline.Process(LinkContext context) (TaskId:87)
                        at Mono.Linker.Driver.Run(ILogger customLogger) (TaskId:87)
                        at Mono.Linker.Driver.Main(String[] args) (TaskId:87)
                     The command exited with code 134. (TaskId:87)
                     Output Property: _ILLinkExitCode=134

It also however, highlighted a problem with the Resource Designer Assembly. Looking at the output for the test app it turns out the final assembly does NOT include the expected anim based resources.
Looking at the IL we found that the properties were NOT being fixed up to use the correct casing. So we have enterfromright instead of EnterFromRight. Further investigation tracked the issue down to the RTxtParser. This class uses the case_map.txt file to lookup. The case_map.txt file contains entries such as

animation/enterfromleft;animation/EnterFromLeft
animation/enterfromright;animation/EnterFromRight

these allow use to map the "android" lower cased items to the C# cased items.
The problem was we were not mapping anim to animation. There is a method called ResourceParser.GetNestedTypeName which is used to map the android resource type to the
managed resource type. For example it maps anim to Animation and bool to Boolean.
This was not being called when we tried to map the resource. As a result we never found the correct
cased entry. This would result in the final Resource Designer Assembly containing the lower cased "android"
naming of the property and not the correctly cased one which the C#/IL would be using. So the fields were never
fixed up.

So in this case the fix is to make sure we call ResourceParser.GetNestedTypeName when calculating the final property name in the RTxtParser.

[jonathanpeppers]

Otherwise, looks good to me -- we have a test that runs an app, verifying it no longer crashes. 👍

[jonpryor]

If ILLINK is not defined, we should be within Xamarin.Android.Build.Tasks.dll, right? In which case we should have a "real" MSBuild Task that can raise "real" MSBuild error messages, instead of going through Console.Error.WriteLine()?

[dellis1972]

This is done in https://github.com/xamarin/xamarin-android/pull/8066/files#diff-6bfa8cb4f52234d33d427a9aa52682179ea4e86d986fa7b2c6c26504ffcd6d96R145 by overriding this method. The Console.Error.WriteLine here is just a backup.

[jonpryor]

Probably not related to this PR, but why'd the package size increase so much?

[dellis1972]

Looks like its

"assemblies/System.Private.CoreLib.dll": {
      "Size": 516811
      "Size": 536436
    },

or at least a fair chunk of it will be

[jonpryor]

…and this one shrank. Nice! …but weird?

[jonpryor]

[Xamarin.Android.Build.Tasks] missing resource error handling (#8066)

Context: https://github.com/mono/SkiaSharp/issues/2444
Context: https://github.com/mono/SkiaSharp/pull/2465
Context: fcd7cf8f4200ccae92e333c920613bfec260973b
Context: dc3ccf28cdbe9f8c0a705400b83c11a85c81a980
Context: 3ec1b159b8125cfaea1d774da94b323f08e2432b

In Classic Xamarin.Android, `@(AndroidResource)` files were embedded
into assemblies as `@(EmbeddedResource)` entries.  While convenient,
this slowed down build times (as every assembly needed to be checked
to see if it had embedded resources), and this functionality was
removed for .NET 6 in fcd7cf8f.  The replacement was to use `.aar`
files, typically located in the same directory as the assembly.

Unfortunately, it was easy to incorrectly migrate from the old system
to the new system, which was the case for the 
[SkiaSharp.Views (v2.88.3) NuGet Package][0], which *uses* an
[`@attr/ignorePixelScaling`][1], but did not package it.

In .NET 6 and 7, this was "fine" *so long as* that resource value was
never used.  If it *was* used, then the results were undefined: a
"garbage" resource id value would be used, which would either be
invalid or refer to a *different* resource altogether!

.NET 8 introduces the Resource Designer Assembly (dc3ccf28), which
involves *rewriting non-.NET 8 assemblies* to use the Resource
Designer Assembly, which in turn requires that all resources exist.

Which brings us to mono/SkiaSharp#2444: because the `SkiaSharp.Views`
NuGet package references but did not redistribute the
`@attr/ignorePixelScaling` resource, the assembly rewriter would
*skip over* the missing resource name, resulting in an invalid
assembly.  This in turn would result in a *runtime crash*:

	System.BadImageFormatException: 'Invalid field token 0x040000a1'

We decided that instead of ignoring missing resource fields, we
should error out.

Update `FixLegacyResourceDesignerStep` to throw an exception if we
cannot find the required Resource Designer Assembly property which
matches a "legacy" field.

In Debug builds, this will result in the build-time error:

	error XA8000: Could not find Android Resource '@attr/ignorePixelScaling'.
	Please update @(AndroidResource) to add the missing resource.

For Release builds, this instead results in an IL8000 error:

	error IL8000: Could not find Android Resource '@attr/ignorePixelScaling'.
	Please update @(AndroidResource) to add the missing resource.

Note that this only moves a runtime error to a compile-time error.
The fix for mono/SkiaSharp#2444 is mono/SkiaSharp#2465, which adds
`SkiaSharp.Views.Android.aar` to the `SkiaSharp.Views` NuGet package.
This should be fixed in the (forthcoming) SkaSharp.Views 2.88.4.
[A *workaround* for mono/SkiaSharp#2444][3] is to define the
`@attr/ignorePixelScaling` resource within your app project.

Additionally, we found another problem while investigating
mono/SkiaSharp#2444 around resource name case sensitivity.  Not all
Android Resource names need to be lowercase; generally only those
that are based on *filenames* need to be lowercase, e.g.
`@layout/main`.  Resources which are defined within XML containers,
such as [string resources][2], may contain uppercase letters.
While looking at the output for the test app, it turns out the final
assembly does NOT include the expected `anim` based resources.
Looking at the IL we found that the properties were NOT being fixed
up to use the correct casing, e.g. we have `enterfromright` instead
of `EnterFromRight`.  Further investigation tracked the issue down to
the `RTxtParser`; This class uses the `case_map.txt` file for lookup.
The `case_map.txt` file contains entries such as:

	animation/enterfromleft;animation/EnterFromLeft
	animation/enterfromright;animation/EnterFromRight

these allow us to map the "android" lower cased items to the C# cased
items.   The problem was we were not mapping `anim` to `animation`.
There is a method called `ResourceParser.GetNestedTypeName()` which
is used to map the android resource type to the managed resource type.
For example it maps `anim` to `Animation` and `bool` to `Boolean`.
This was not being called when we tried to map the resource.  As a
result we never found the correct cased entry.  This would result in
the final Resource Designer Assembly containing the lower cased
"android" naming of the property and not the correctly cased one
which the C#/IL would be using; the fields were never fixed up. 

The fix is to make sure we call `ResourceParser.GetNestedTypeName()`
when calculating the final property name in the `RTxtParser`.

[0]: https://www.nuget.org/packages/SkiaSharp/2.88.3
[1]: https://github.com/mono/SkiaSharp/blob/99c2437b1055dc6eb8ee25e90e5ad4afa695aa89/source/SkiaSharp.Views/SkiaSharp.Views.Android/Resources/values/attrs.xml#L4
[2]: https://developer.android.com/guide/topics/resources/string-resource
[3]: https://github.com/mono/SkiaSharp/issues/2444#issuecomment-1564090245