Enable return buffers on Windows ARM64 for struct-returning member functions (#23625)

Enable return buffers on Windows ARM64 for struct-returning member functions (#23625)

* Enable return buffers on Windows ARM64 for struct-returning member functions. Fixes #23577.

* Update comment to match new condition.

* Enable byref return on all Windows (excluding arm64 HFA. Add more test cases for ThisCall.

* On x86, if we have a normalized return value in an instance method, get back the actual type so that we correctly marshal it via a return buffer.

* Fix param ordering.

* Clean up based on PR feedback.

* Fix accidental variable shadowing.