[jdk21u-dev] RFR: 8318986: Improve GenericWaitBarrier performance

[Aleksey Shipilev]

Clean backport to drastically improve safepoint performance under heavy load, fixing regression between JDK 11 and JDK 17.

Additional testing:
 - [x] Ad-hoc performance runs, expected improvements
 - [x] MacOS AArch64 server fastdebug, `tier{1,2,3}`

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Commit messages:
 - Backport 30462f9da40d3a7ec18fcf46e2154fabb5fd4753

Changes: https://git.openjdk.org/jdk21u-dev/pull/70/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=70&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8318986
  Stats: 286 lines in 2 files changed: 225 ins; 12 del; 49 mod
  Patch: https://git.openjdk.org/jdk21u-dev/pull/70.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u-dev.git pull/70/head:pull/70

PR: https://git.openjdk.org/jdk21u-dev/pull/70