RFR: 8342818: Implement CPU Time Profiling for JFR [v7]

[Johannes Bechberger]

> This is the code for the [JEP draft: CPU Time based profiling for JFR].

Johannes Bechberger has updated the pull request incrementally with two additional commits since the last revision:

 - Add test case for class unloading
 - Improve readability of thread_state functions

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Changes:
  - all: https://git.openjdk.org/jdk/pull/20752/files
  - new: https://git.openjdk.org/jdk/pull/20752/files/01783bc9..1929fa94

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=20752&range=06
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=20752&range=05-06

  Stats: 224 lines in 6 files changed: 184 ins; 24 del; 16 mod
  Patch: https://git.openjdk.org/jdk/pull/20752.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/20752/head:pull/20752

PR: https://git.openjdk.org/jdk/pull/20752