[tests] Ignore MarshalMethodsAppRuns on CoreCLR (#12213)

Marshal methods are only supported with MonoVM, which is no longer part
of the main runtime test matrix. Ignore the CoreCLR and NativeAOT cases
until supported coverage is available.

Refs #12206

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

Author: jonathanpeppers

tests/MSBuildDeviceIntegration/Tests/MarshalMethodsGCHangTests.cs

@@ -84,6 +84,7 @@ public override void Close ()
 ";
 
 	[Test]
+	[Ignore ("Marshal methods are not yet working on CoreCLR: https://github.com/dotnet/android/issues/12206")]
 	public void MarshalMethodsAppRuns ([Values (AndroidRuntime.CoreCLR, AndroidRuntime.NativeAOT)] AndroidRuntime runtime)
 	{
 		const bool isRelease = true;