[generator] Fix xamarin-android/src/Mono.Android build

Context: a65d6fb
Context: dotnet/android#6939

dotnet/android#6939 attempted to bump to 05eddd9, which
promptly broke the build of src/Mono.Android, e.g.
`src/Mono.Android/obj/Debug/net6.0/android-32/mcw/Android.Widget.GridLayout.cs`:

	/*       */ partial class GridLayout {
	/*       */     partial class partial class LayoutParams {
	/*       */         [Register ("rowSpec")]
	/*       */         public Android.Widget.GridLayout.Spec? RowSpec {
	/*       */             get {
	/*       */                 const string __id = "rowSpec.Landroid/widget/GridLayout$Spec;";
	/*       */                 var __v = _members.InstanceFields.GetObjectValue (__id, this);
	/*       */                 return global::Java.Lang.Object.GetObject<Android.Widget.GridLayout.Spec> (__v.Handle, JniHandleOwnership.TransferLocalRef);
	/*       */             }
	/*       */             set {
	/*       */                 const string __id = "rowSpec.Landroid/widget/GridLayout$Spec;";
	/*       */                 IntPtr native_value = global::Android.Runtime.JNIEnv.ToLocalJniHandle (value);
	/*       */                 try {
	/* L 239 */                     _members.InstanceFields.SetValue (__id, this, new JniObjectReference (value));
	/*       */                 } finally {
	/* L 242 */                     global::Android.Runtime.JNIEnv.DeleteLocalRef (value);
	/*       */                 }
	/*       */             }
	/*       */         }
	/*       */     }
	/*       */ }

due to compilation errors:

	src/Mono.Android/obj/Debug/net6.0/android-32/mcw/Android.Widget.GridLayout.cs(239,77):
	  error CS1503: Argument 1: cannot convert from 'Android.Widget.GridLayout.Spec' to 'System.IntPtr'
	src/Mono.Android/obj/Debug/net6.0/android-32/mcw/Android.Widget.GridLayout.cs(242,54):
	  error CS1503: Argument 1: cannot convert from 'Android.Widget.GridLayout.Spec' to 'System.IntPtr'

This was caused by `BoundFieldAsProperty.cs` not appropriately
setting `arg` to `native_arg`, so that the correct variable would be
cleaned up in the `finally` block.

There was another set of errors:

	src/Mono.Android/obj/Release/net6.0/android-32/mcw/Android.Widget.ArrayAdapter.cs(525,53):
	  error CS1503: Argument 1: cannot convert from 'Java.Lang.ICharSequence[]' to 'string[]?'

which was also caused by a65d6fb mis-refactoring
`SourceWriterExtensions.cs`, and overlooking the entire existence of
the `CharSequence.ArrayToStringArray()` method (oops).

Update `generator` so that xamarin-android once again builds.

Author: jonpryor

tools/generator/CodeGenerationOptions.cs

@@ -309,6 +309,13 @@ public string GetStringArrayToCharSequenceArrayMethodName ()
 				? "ICharSequenceExtensions.ToCharSequenceArray"
 				: "CharSequence.ArrayFromStringArray";
 		}
+
+		public string GetCharSequenceArrayToStringArrayMethodName ()
+		{
+			return CodeGenerationTarget == CodeGenerationTarget.JavaInterop1
+				? "ICharSequenceExtensions.ToStringArray"
+				: "CharSequence.ArrayToStringArray";
+		}
 	}
 }
 

tools/generator/SourceWriters/BoundFieldAsProperty.cs

@@ -144,11 +144,13 @@ protected override void WriteSetterBody (CodeWriter writer)
 				if (opt.CodeGenerationTarget != CodeGenerationTarget.JavaInterop1 &&
 						field.SetParameters.HasCleanup &&
 						!have_prep) {
+					arg = native_arg;
 					writer.WriteLine ($"IntPtr {native_arg} = global::Android.Runtime.JNIEnv.ToLocalJniHandle (value);");
 				}
 			}
 
 			writer.WriteLine ("try {");
+
 			writer.Write ($"\t_members.{indirect}.SetValue (__id{(field.IsStatic ? "" : ", this")}, ");
 
 			if (opt.CodeGenerationTarget == CodeGenerationTarget.JavaInterop1) {
@@ -161,7 +163,6 @@ protected override void WriteSetterBody (CodeWriter writer)
 			} else {
 				writer.WriteLine ($"{(invokeType != "Object" ? arg : "new JniObjectReference (" + arg + ")")});");
 			}
-			writer.WriteLine ();
 
 			writer.WriteLine ("} finally {");
 			writer.Indent ();

tools/generator/SourceWriters/Extensions/SourceWriterExtensions.cs

@@ -367,7 +367,7 @@ public static void WriteMethodStringOverloadBody (CodeWriter writer, Method meth
 				case "void":
 					break;
 				case "Java.Lang.ICharSequence[]":
-					writer.WriteLine ($"var __rsval = {opt.GetStringArrayToCharSequenceArrayMethodName ()} (__result);");
+					writer.WriteLine ($"var __rsval = {opt.GetCharSequenceArrayToStringArrayMethodName ()} (__result);");
 					break;
 				case "Java.Lang.ICharSequence":
 					writer.WriteLine ("var __rsval = __result?.ToString ();");