[TrimmableTypeMap] Use JniNativeMethod for RegisterNatives bootstrap

[simonrozsival]

Summary

Refactor the mono.android.Runtime.registerNatives bootstrap registration in TrimmableTypeMap to use zero-allocation JNI interop:

• Use JniNativeMethod struct with fixed UTF-8 string literals instead of JniNativeMethodRegistration + delegate wrapper
• Use [UnmanagedCallersOnly] on OnRegisterNatives callback (no Delegate allocation, no GC handle)
• Use JniType UTF-8 constructor ("mono/android/Runtime"u8) to avoid string-to-UTF8 conversion at runtime
• Remove RegisterMethod helper (already removed in a separate PR)

Changes

File	Change
TrimmableTypeMap.cs	RegisterNatives(): use JniNativeMethod + fixed UTF-8 literals + [UnmanagedCallersOnly] callback; remove old delegate-based registration and RegisterMethod helper

[Copilot]

Pull request overview

Replace the Marshal.GetDelegateForFunctionPointer-based bootstrap registration for mono.android.Runtime.registerNatives with a zero-allocation registration path using JniNativeMethod and the new RegisterNatives(ReadOnlySpan<JniNativeMethod>) overload.

Changes:

• Update RegisterNatives() to use fixed UTF-8 strings + stackalloc JniNativeMethod instead of allocating a delegate wrapper.
• Switch to the span-based JniEnvironment.Types.RegisterNatives overload.
• Bump external/Java.Interop submodule to a revision that provides JniNativeMethod and the span overload.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
src/Mono.Android/Microsoft.Android.Runtime/TrimmableTypeMap.cs	Reworks bootstrap RegisterNatives() to use stackalloc + span-based JNI registration.
external/Java.Interop	Updates submodule commit to pick up the new JniNativeMethod API surface.

[simonrozsival]

🤖 AI Review Summary

Verdict: ✅ LGTM

Found 0 issues.

Clean, minimal change: replaces Marshal.GetDelegateForFunctionPointer + JniNativeMethodRegistration with JniNativeMethod stackalloc + ReadOnlySpan<JniNativeMethod> for zero-allocation JNI native method registration. JniType("..."u8) avoids string→UTF-8 conversion.

👍 Good use of fixed + stackalloc for the blittable JNI struct — matches the pattern used by generated proxy RegisterNatives methods. Submodule bump is justified (picks up JniNativeMethod struct and span overload from dotnet/java-interop#1393).

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Review generated by android-reviewer from review guidelines.

[simonrozsival]

🤖 AI Review Summary

Verdict: ✅ LGTM

Found 0 issues.

Clean, focused refactoring of the RegisterNatives bootstrap in TrimmableTypeMap:

• 👍 Zero-allocation path: JniNativeMethod struct + [UnmanagedCallersOnly] replaces the delegate-based JniNativeMethodRegistration — eliminates Delegate allocation and GC handle.
• 👍 UTF-8 literals ("mono/android/Runtime"u8) avoid runtime string-to-UTF8 conversion.
• 👍 fixed scope correctly pins the UTF-8 byte pointers for the lifetime of the RegisterNatives JNI call.
• 👍 Collection expression [method] is clean and idiomatic for the single-element ReadOnlySpan<JniNativeMethod>.

⏳ CI is still pending — all Azure DevOps checks are in progress. Verify CI passes before merging.

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Review generated by android-reviewer from review guidelines.