Revert "Revert "Update xUnit.v3 to support MTP tests (#9261)" (#9336)" (#9337)

The earlier revert was incorrect. That wasn't commit responsible for
breaking the build. It was:
```
commit 6ca2de9
Author: Ankit Jain <[email protected]>
Date:   Wed May 14 11:39:18 2025 -0400

    [CI] Add PR validation on macOS (#9287)
```

This reverts commit 3850afa.

Author: radical

.vscode/settings.json

@@ -1,6 +1,6 @@
 {
     "dotnet.previewSolution-freeWorkspaceMode": true,
+    "dotnet.testWindow.useTestingPlatformProtocol": true,
     "dotnet.defaultSolution": "./Aspire.slnx",
-    "dotnet.preview.enableSupportForSlnx": true,
-    "dotnet.testWindow.useTestingPlatformProtocol": false
+    "dotnet.preview.enableSupportForSlnx": true
 }

eng/Versions.props

@@ -12,9 +12,9 @@
     <DotNetRuntimePreviousVersionForTesting>8.0.13</DotNetRuntimePreviousVersionForTesting>
     <!-- dotnet 8.0 versions for running tests - used for templates tests -->
     <DotNetSdkPreviousVersionForTesting>8.0.406</DotNetSdkPreviousVersionForTesting>
-    <XunitV3Version>2.0.0</XunitV3Version>
-    <XUnitAnalyzersVersion>1.20.0</XUnitAnalyzersVersion>
-    <XunitRunnerVisualStudioVersion>3.0.2</XunitRunnerVisualStudioVersion>
+    <XunitV3Version>2.0.2</XunitV3Version>
+    <XUnitAnalyzersVersion>1.21.0</XUnitAnalyzersVersion>
+    <XunitRunnerVisualStudioVersion>3.1.0</XunitRunnerVisualStudioVersion>
     <MicrosoftTestingPlatformVersion>1.6.3</MicrosoftTestingPlatformVersion>
     <MicrosoftNETTestSdkVersion>17.13.0</MicrosoftNETTestSdkVersion>
     <!-- Enable to remove prerelease label. -->