RFR: 8335779: JFR: Hide sleep events

[Erik Gahlin]

Could I have review of an enhancement that hides remaining "threads sleep" events in the JFR code. This is to reduce the noise some users experience.

Testing: jdk/jdk/jfr/* + 1500 *  jdk/jdk/jfr/jvm/TestHiddenEvent.java

Thanks
Erik

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Commit messages:
 - Initial

Changes: https://git.openjdk.org/jdk/pull/20075/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=20075&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8335779
  Stats: 301 lines in 15 files changed: 170 ins; 78 del; 53 mod
  Patch: https://git.openjdk.org/jdk/pull/20075.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/20075/head:pull/20075

PR: https://git.openjdk.org/jdk/pull/20075