MethodHandles: Support and tests for revealDirect / reflectAs.

We need runtime support to materialize a Constructor, Field or
Method object from a MethodHandle and its associated ArtField
or ArtMethod pointer.

An alternate approach might be to have all handles hold a reference
to their associated Field or Method object (in addition to the
raw ArtField or ArtMethod) but that seems unnecessary given that
these APIs are not expected to be called often.

Test: test-art-host

Change-Id: I9450706b9c30359edebf2e8a7afbc8d89bd68b26
7 files changed