RFR: 8308400: add ForceEarlyReturn support for virtual threads [v3]

[Serguei Spitsyn]

> This enhancement adds ForceEarlyReturnXXX support for virtual threads. The spec defines minimal support that the JVMTI ForceEarlyReturnXXX can be used for a virtual thread suspended an an event.
> Actually, the ForceEarlyReturnXXX can supports suspended and mounted virtual threads.
> 
> CSR (approved): https://bugs.openjdk.org/browse/JDK-8308401 add ForceEarlyReturn support for virtual threads
> 
> Testing:
> New test was developed: serviceability/vthread/ForceEarlyReturnTest.
> Submitted mach5 tiers 1-6 are good.
> TBD: rerun mach5 tiers 1-6 at the end of review again if necessary.

Serguei Spitsyn has updated the pull request incrementally with one additional commit since the last revision:

  addressed review comment about test formatting

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/14067/files
  - new: https://git.openjdk.org/jdk/pull/14067/files/498ae392..64d234b1

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=14067&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=14067&range=01-02

  Stats: 3 lines in 1 file changed: 0 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/14067.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/14067/head:pull/14067

PR: https://git.openjdk.org/jdk/pull/14067