A lot of changes have accumulated in the loom repo, some of these changes (particularly tests) should be brought to the main line. The following can be safely moved to main line:

Implementation:
Robustness improvements to avoid OOME when unparking a virtual thread.
Robustness improvements to reduce class loading when a virtual thread parks or parks when pinned.
VirtualThread changes to reduce contention on timer queues when doing timed-park.

Tests:
New tests for object monitors (this is a subset of the tests in the loom repo)
New test infrastructure to allow tests use a custom scheduler
More test scenarios added to ThreadAPI and JVMTI GetThreadStateTest.java
New test for ThreadMXBean.getLockedMonitor with synchronized native methods
Reimplement of JVMTI VThreadEvent test to improve reliability
Rename some tests to get consistent naming
Diagnostic output in several stress tests to help trace progress in the event of a timeout