RFR: 8308400: add ForceEarlyReturn support for virtual threads [v5]

[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:

  review: refactor common PopFrame/ForceEarlyReturn fragments to separate function

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Changes:
  - all: https://git.openjdk.org/jdk/pull/14067/files
  - new: https://git.openjdk.org/jdk/pull/14067/files/c01fcdba..85444759

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=14067&range=04
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=14067&range=03-04

  Stats: 63 lines in 4 files changed: 29 ins; 22 del; 12 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