ART: Extend Object tag table to be explicitly lockable

Expose the lock for the system weak holder. Add functions to lock
and unlock the object tagging table, and add accessors that assume
the table is already locked.

Bug: 31385354
Test: m test-art-host
Change-Id: I5a4328b0d439d13e6ace7965e22f01bbf8130f20
3 files changed