[jdk22u] RFR: 8327501: Common ForkJoinPool prevents class unloading in some cases

[Aleksey Shipilev]

First change fixes the regression since JDK 19. Second change fixes the regression from the fix.

Additional testing:
 - [x] Linux x86_64 server fastdebug, `all`

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Commit messages:
 - Backport 28216aa971ea65938117107542152abd532a5384
 - Backport 53c4714aab2e072ba18631875dcaa3b2d5d22243

Changes: https://git.openjdk.org/jdk22u/pull/206/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk22u&pr=206&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8327501
  Stats: 11 lines in 2 files changed: 8 ins; 2 del; 1 mod
  Patch: https://git.openjdk.org/jdk22u/pull/206.diff
  Fetch: git fetch https://git.openjdk.org/jdk22u.git pull/206/head:pull/206

PR: https://git.openjdk.org/jdk22u/pull/206