[ci] Move Windows build and test to VS2019

We've been encountering a handful of issues recently with the Windows
machine pool we're using for building and testing. There have been quite
a few failures caused by files being locked, or dependencies being out
of date or missing. Moving to the VSEng VS2019 Windows pool will
hopefully resolve some of these issues.

Unfortunately the size of our build dependencies presents an issue when
attempting to use the Microsoft hosted Windows VS2019 agents, as our Win
job ultimately runs out of space when executing on those VMS. Using the
VSEng VS2019 pool will allow us to migrate to VS2019 while avoiding disk
space limitations.

Author: pjcollins

build-tools/automation/azure-pipelines.yaml

@@ -21,7 +21,9 @@ variables:
   InstallerArtifactName: installers
   TestAssembliesArtifactName: test-assemblies
   NUnitConsoleVersion: 3.9.0
+  DotNetCoreVersion: 2.1.701
   HostedWinVS2019: Hosted Windows 2019 with VS2019
+  VSEngWinVS2019: VSEng-MicroBuildVS2019
 
 # Stage and Job "display names" are shortened because they are combined to form the name of the corresponding GitHub check.
 stages:
@@ -54,9 +56,9 @@ stages:
       submodules: recursive
 
     - task: UseDotNet@2
-      displayName: install .NET Core 2.1.701
+      displayName: install .NET Core $(DotNetCoreVersion)
       inputs:
-        version: 2.1.701
+        version: $(DotNetCoreVersion)
 
       # Update Mono in a separate step since xaprepare uses it as well and it will crash when Mono it runs with is updated
       # The 'prepare' step creates the bundle
@@ -103,9 +105,9 @@ stages:
       submodules: recursive
 
     - task: UseDotNet@2
-      displayName: install .NET Core 2.1.701
+      displayName: install .NET Core $(DotNetCoreVersion)
       inputs:
-        version: 2.1.701
+        version: $(DotNetCoreVersion)
 
     - task: DownloadPipelineArtifact@1
       inputs:
@@ -198,7 +200,7 @@ stages:
   - job: queue_vsix_signing
     displayName: Queue Vsix Signing
     dependsOn: mac_build_create_installers
-    pool: $(XA.Build.Win.Pool)
+    pool: $(VSEngWinVS2019)
     condition: and(eq(dependencies.mac_build_create_installers.result, 'Succeeded'), eq(variables['XA.Commercial.Build'], 'true'), ne(variables['Build.Reason'], 'PullRequest'))
     timeoutInMinutes: 45
     cancelTimeoutInMinutes: 1
@@ -226,7 +228,7 @@ stages:
   jobs:
   - job: win_build_test
     displayName: Build and Test
-    pool: $(XA.Build.Win.Pool)
+    pool: $(VSEngWinVS2019)
     timeoutInMinutes: 360
     cancelTimeoutInMinutes: 5
     workspace:
@@ -240,6 +242,11 @@ stages:
     - checkout: self
       submodules: recursive
 
+    - task: UseDotNet@2
+      displayName: install .NET Core $(DotNetCoreVersion)
+      inputs:
+        version: $(DotNetCoreVersion)
+
     - task: DownloadPipelineArtifact@1
       inputs:
         artifactName: $(BundleArtifactName)

build-tools/automation/yaml-templates/mac/setup-test-environment.yaml

@@ -18,9 +18,9 @@ steps:
   displayName: install xaprepare dependencies
 
 - task: UseDotNet@2
-  displayName: install .NET Core 2.1.701
+  displayName: install .NET Core $(DotNetCoreVersion)
   inputs:
-    version: 2.1.701
+    version: $(DotNetCoreVersion)
 
 # Restore solutions for Xamarin.Android.Tools.sln, Xamarin.Android.sln, and Xamarin.Android-Tests.sln
 - task: NuGetCommand@2