method_handles: Complete support for emulated stack frames.

Most of this change is a refactor that templatizes the code
that performs argument conversions. This allows us to copy arguments
between two shadow frames, or an emulated stack frame and a shadow
frame.

Test: make test-art-host
Bug: 30550796

Change-Id: I23e65735a2dbd28f3c7b7d1ccf9762e77e0cf1f1