Enable more VarHandle tests

Enables all of the upstream VarHandle tests aside from those depending
on ByteBuffer updates.

Fix for MethodHandles.Lookup.revealDirect() when MH kind is a
VarHandle invoker.

Access check fix in MethodHandles.reflectAs().

Bug: 206407164
Bug: 203822478
Test: atest CtsLibcoreTestCases
Change-Id: Iacc4ffac2157b14a0252714126910f7ccd981b8c
4 files changed