RFR: 8352066: JVM.commit() and JVM.flush() exhibit race conditions against JFR epochs

[Markus Grönlund]

Greetings,

This change set removes some race conditions involving JFR epochs. For details, please see the JIRA issue.

Testing: jdk_jfr, TestChunkIntegrity testing

Thanks
Markus

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Commit messages:
 - 8352066

Changes: https://git.openjdk.org/jdk/pull/24061/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=24061&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8352066
  Stats: 64 lines in 9 files changed: 5 ins; 36 del; 23 mod
  Patch: https://git.openjdk.org/jdk/pull/24061.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/24061/head:pull/24061

PR: https://git.openjdk.org/jdk/pull/24061