[Xamarin.Android.Build.Tasks] RemoveRegisterAttr IAssemblyResolver (#9803)

Fixes? #9629

In #9629 the customer reports a build failure:

	XARRA7028: Mono.Cecil.AssemblyResolutionException: Failed to resolve assembly: 'System.Private.CoreLib, Version=9.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e'
	   bei Mono.Cecil.BaseAssemblyResolver.Resolve(AssemblyNameReference name, ReaderParameters parameters)
	   bei Mono.Cecil.DefaultAssemblyResolver.Resolve(AssemblyNameReference name)
	   bei Mono.Cecil.MetadataResolver.Resolve(TypeReference type)
	   bei Mono.Cecil.TypeReference.Resolve()
	   bei Mono.Cecil.Mixin.CheckedResolve(TypeReference self)
	   bei Mono.Cecil.MetadataBuilder.GetConstantType(TypeReference constant_type, Object constant)
	   bei Mono.Cecil.MetadataBuilder.AddConstant(IConstantProvider owner, TypeReference type)
	   bei Mono.Cecil.MetadataBuilder.AddField(FieldDefinition field)
	   bei Mono.Cecil.MetadataBuilder.AddFields(TypeDefinition type)
	   bei Mono.Cecil.MetadataBuilder.AddType(TypeDefinition type)
	   bei Mono.Cecil.MetadataBuilder.AddTypes()
	   bei Mono.Cecil.MetadataBuilder.BuildTypes()
	   bei Mono.Cecil.MetadataBuilder.BuildModule()
	   bei Mono.Cecil.MetadataBuilder.BuildMetadata()
	   bei Mono.Cecil.ModuleWriter.<>c.<BuildMetadata>b__2_0(MetadataBuilder builder, MetadataReader _)
	   bei Mono.Cecil.ModuleDefinition.Read[TItem,TRet](TItem item, Func`3 read)
	   bei Mono.Cecil.ModuleWriter.Write(ModuleDefinition module, Disposable`1 stream, WriterParameters parameters)
	   bei Mono.Cecil.ModuleWriter.WriteModule(ModuleDefinition module, Disposable`1 stream, WriterParameters parameters)
	   bei Mono.Cecil.ModuleDefinition.Write(Stream stream, WriterParameters parameters)
	   bei Xamarin.Android.Tasks.RemoveRegisterAttribute.RunTask() in /Users/runner/work/1/s/xamarin-android/src/Xamarin.Android.Build.Tasks/Tasks/RemoveRegisterAttribute.cs:Zeile 33.
	   bei Microsoft.Android.Build.Tasks.AndroidTask.Execute() in /Users/runner/work/1/s/xamarin-android/external/xamarin-android-tools/src/Microsoft.Android.Build.BaseTasks/AndroidTask.cs:Zeile 25.

We are unable to reproduce this, and the scenario doesn't quite make
sense to us: the `<RemoveRegisterAttribute/>` task operates on post-
trimmed assemblies, *nearly all of which* will contain a reference to
`System.Private.CorLib.dll` [^1].  Why does this work of us (and CI!
and most other customers!) and fail in this instance?

¯\\_(ツ)_/¯

Meanwhile, we do know of a plausible "fix"/"workaround": add the use
of a `DirectoryAssemblyResolver` which contains the directory
containing the assembly we're processing.
The `$(IntermediateOutputPath)android-*/linked/shrunk` should also
contain a `System.Private.CoreLib.dll` [^1], which will allow it to
be resolved, thus avoiding the `AssemblyResolutionException`.

[^1]: Consider:
      ```
      for a in obj/Release/net9.0-android/android-arm64/linked/shrunk/*.dll ; do \
        echo "Assembly: $a" ; \
        monodis --assemblyref $a | grep System.Private.CoreLib ; \
        done
      Assembly: obj/Release/net9.0-android/android-arm64/linked/shrunk/Java.Interop.dll
        Name=System.Private.CoreLib
      Assembly: obj/Release/net9.0-android/android-arm64/linked/shrunk/Mono.Android.Runtime.dll
        Name=System.Private.CoreLib
      Assembly: obj/Release/net9.0-android/android-arm64/linked/shrunk/Mono.Android.dll
        Name=System.Private.CoreLib
      Assembly: obj/Release/net9.0-android/android-arm64/linked/shrunk/System.Console.dll
        Name=System.Private.CoreLib
      Assembly: obj/Release/net9.0-android/android-arm64/linked/shrunk/System.Linq.dll
        Name=System.Private.CoreLib
      Assembly: obj/Release/net9.0-android/android-arm64/linked/shrunk/System.Private.CoreLib.dll
      Assembly: obj/Release/net9.0-android/android-arm64/linked/shrunk/System.Runtime.InteropServices.dll
        Name=System.Private.CoreLib
      Assembly: obj/Release/net9.0-android/android-arm64/linked/shrunk/System.Runtime.dll
        Name=System.Private.CoreLib
      Assembly: obj/Release/net9.0-android/android-arm64/linked/shrunk/_Microsoft.Android.Resource.Designer.dll
        Name=System.Private.CoreLib
      Assembly: obj/Release/net9.0-android/android-arm64/linked/shrunk/net9-android.dll
        Name=System.Private.CoreLib
      ```

Author: dellis1972

src/Xamarin.Android.Build.Tasks/Tasks/RemoveRegisterAttribute.cs

@@ -8,6 +8,7 @@
 using Microsoft.Build.Utilities;
 using Mono.Cecil;
 using Microsoft.Android.Build.Tasks;
+using Java.Interop.Tools.Cecil;
 
 namespace Xamarin.Android.Tasks
 {
@@ -24,8 +25,11 @@ public override bool RunTask ()
 		{
 			// Find Mono.Android.dll
 			var mono_android = ShrunkFrameworkAssemblies.First (f => Path.GetFileNameWithoutExtension (f.ItemSpec) == "Mono.Android").ItemSpec;
-
-			using (var assembly = AssemblyDefinition.ReadAssembly (mono_android, new ReaderParameters { ReadWrite = true })) {
+			var path = Path.GetFullPath (Path.GetDirectoryName (mono_android));
+			using var resolver = new DirectoryAssemblyResolver (this.CreateTaskLogger (), loadDebugSymbols: false, loadReaderParameters: new ReaderParameters { ReadWrite = true });
+			resolver.SearchDirectories.Add (path);
+			
+			using (var assembly = resolver.Load (mono_android)) {
 				// Strip out [Register] attributes
 				foreach (TypeDefinition type in assembly.MainModule.Types)
 					ProcessType (type);