Add support for JVMTI GetObjectMonitorUsage function.

Adds support for the can_get_monitor_info capability and all
associated functionality. Also fixes a minor bug where monitor info
incorrectly said that an unlocked monitor had 1 entry in some cases.

Test: ./test.py --host -j50
Test: art/tools/run-jdwp-tests --mode=host

Bug: 62821960
Bug: 34409230

Change-Id: I9a4817ea309aaf94c56e9c0a694b88c93e7b629c