[jdk21] RFR: 8311556: GetThreadLocalStorage not working for vthreads mounted during JVMTI attach

[Serguei Spitsyn]

Clean backport from mainline jdk repo to jdk21 for the fix of:
[8311556](https://bugs.openjdk.org/browse/JDK-8311556): GetThreadLocalStorage not working for vthreads mounted during JVMTI attach

Testing:
 - TBD: mach5 tiers 1-5

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Commit messages:
 - Backport 11a5115caf179a1bbed5311e12ed3851e026c5c5

Changes: https://git.openjdk.org/jdk21/pull/117/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk21&pr=117&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8311556
  Stats: 196 lines in 3 files changed: 181 ins; 13 del; 2 mod
  Patch: https://git.openjdk.org/jdk21/pull/117.diff
  Fetch: git fetch https://git.openjdk.org/jdk21.git pull/117/head:pull/117

PR: https://git.openjdk.org/jdk21/pull/117