[NativeAOT] Forward JCW Java annotations

[jonathanpeppers]

Fixes #12542

Summary

• forward Java annotations from managed custom attributes through the trimmable NativeAOT JCW pipeline
• preserve annotations on types, methods, registered constructors, property overrides, and exported fields
• cache annotation metadata and support cross-assembly attribute definitions such as Android.Webkit.JavascriptInterfaceAttribute
• add regression coverage matching the app-to-Mono.Android assembly boundary

Testing

• dotnet test tests\Microsoft.Android.Sdk.TrimmableTypeMap.Tests\Microsoft.Android.Sdk.TrimmableTypeMap.Tests.csproj -v minimal (773 passed)

[Copilot]

Pull request overview

This PR restores/extends forwarding of Java annotations from managed custom attributes into generated Java Callable Wrappers (JCWs) for the trimmable NativeAOT pipeline, including support for cross-assembly attribute definitions and additional member kinds.

Changes:

• Add JavaAnnotationParser and plumb parsed annotations through the scanner model (JavaPeerInfo, MarshalMethodInfo, etc.).
• Emit parsed annotations in the JCW Java source generator for types, constructors, methods, and exported fields.
• Add new fixture assemblies + regression tests covering cross-assembly annotation attributes (e.g., Android.Webkit.JavascriptInterfaceAttribute) and member scenarios (property override getter, constructor, export field).

Reviewed changes

Copilot reviewed 13 out of 13 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
tests/Microsoft.Android.Sdk.TrimmableTypeMap.Tests/TestFixtures/TestTypes.cs	Adds new managed fixture types/members exercising annotation forwarding scenarios (including JavascriptInterface).
tests/Microsoft.Android.Sdk.TrimmableTypeMap.Tests/TestFixtures/TestFixtures.csproj	References the new attribute-fixture project so fixture compilation can use cross-assembly attribute types.
tests/Microsoft.Android.Sdk.TrimmableTypeMap.Tests/TestFixtures/StubAttributes.cs	Removes local stub attribute definitions now provided by the new shared attribute-fixture assembly.
tests/Microsoft.Android.Sdk.TrimmableTypeMap.Tests/TestAttributeFixtures/TestAttributeFixtures.csproj	New project producing a dedicated assembly containing annotation/attribute type definitions for cross-assembly testing.
tests/Microsoft.Android.Sdk.TrimmableTypeMap.Tests/TestAttributeFixtures/Attributes.cs	Defines AnnotationAttribute, RegisterAttribute, JavascriptInterfaceAttribute, and a custom annotation attribute with properties.
tests/Microsoft.Android.Sdk.TrimmableTypeMap.Tests/Microsoft.Android.Sdk.TrimmableTypeMap.Tests.csproj	Ensures the new fixture assembly is built and copied beside the test output for scanner input.
tests/Microsoft.Android.Sdk.TrimmableTypeMap.Tests/Generator/JcwJavaSourceGeneratorTests.cs	Adds assertions that generated Java includes expected forwarded annotations across multiple member kinds.
tests/Microsoft.Android.Sdk.TrimmableTypeMap.Tests/Generator/FixtureTestBase.cs	Updates fixture scanning to include both fixture assemblies as scanner inputs.
src/Microsoft.Android.Sdk.TrimmableTypeMap/Scanner/JavaPeerScanner.cs	Integrates annotation parsing into scan results for types, methods/ctors, property overrides, and export fields.
src/Microsoft.Android.Sdk.TrimmableTypeMap/Scanner/JavaPeerInfo.cs	Extends scan model with JavaAnnotationInfo and annotation collections for relevant entities.
src/Microsoft.Android.Sdk.TrimmableTypeMap/Scanner/JavaAnnotationParser.cs	New parser that detects annotation-decorated attributes and extracts Java annotation names + property assignments.
src/Microsoft.Android.Sdk.TrimmableTypeMap/Scanner/AssemblyIndex.cs	Extends export metadata with IsField to support correct annotation routing for export fields.
src/Microsoft.Android.Sdk.TrimmableTypeMap/Generator/JcwJavaSourceGenerator.cs	Emits forwarded annotations into generated .java source for types/members/fields.