JDK-8308400 improved JVMTI ForceEarlyReturn support for virtual threads. The spec now says it is supported if the thread is suspended at an event (not a specific event as previously spec'd), and additional support may also be provided. The implementation now just requires that the virtual thread be mounted, so this covers being suspended at an event, but also other situations in which the virtual thread is mounted.

JDWP and JDI need to line up with JVMTI. It looks like only spec changes will be needed, but we currently don't have test coverage for the "mounted but not at an event" case, so additional tests will be needed also.