RFR: 8342818: Implement CPU Time Profiling for JFR [v39]

[Johannes Bechberger]

> This is the code for the [JEP draft: CPU Time based profiling for JFR].
> 
> Currently tested using [this test suite](https://github.com/parttimenerd/basic-profiler-tests).

Johannes Bechberger has updated the pull request incrementally with one additional commit since the last revision:

  Don't record exiting threads

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/20752/files
  - new: https://git.openjdk.org/jdk/pull/20752/files/53a2560d..18ec3811

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=20752&range=38
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=20752&range=37-38

  Stats: 7 lines in 2 files changed: 5 ins; 0 del; 2 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