RFR: 8308000: add PopFrame support for virtual threads

[Serguei Spitsyn]

This enhancement adds PopFrame support for virtual threads.

CSR: https://bugs.openjdk.org/browse/JDK-8308001: add PopFrame support for virtual threads

Testing:
New test was developed: `serviceability/vthread/PopFrameTest`.
Submitted mach5 tiers 1-6 are good.
TBD: rerun mach5 tiers 1-6 at the end of review again if necessary.

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Commit messages:
 - 8308000: add PopFrame support for virtual threads

Changes: https://git.openjdk.org/jdk/pull/14002/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=14002&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8308000
  Stats: 469 lines in 5 files changed: 458 ins; 5 del; 6 mod
  Patch: https://git.openjdk.org/jdk/pull/14002.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/14002/head:pull/14002

PR: https://git.openjdk.org/jdk/pull/14002