[jdk20u] RFR: 8305994: Guarantee eventual async monitor deflation

[Aleksey Shipilev]

Clean backport, but waiting for upstream to pass more testing.

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Commit messages:
 - Backport 6b81342c2215041dbb7e9020a67cdc56976c97b1

Changes: https://git.openjdk.org/jdk20u/pull/61/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk20u&pr=61&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8305994
  Stats: 274 lines in 4 files changed: 269 ins; 2 del; 3 mod
  Patch: https://git.openjdk.org/jdk20u/pull/61.diff
  Fetch: git fetch https://git.openjdk.org/jdk20u.git pull/61/head:pull/61

PR: https://git.openjdk.org/jdk20u/pull/61