RFR: 8342818: Implement JEP 509: JFR CPU-Time Profiling [v8]

[Johannes Bechberger]

> This is the code for the [JEP 509: CPU Time based profiling for JFR](https://openjdk.org/jeps/509).
> 
> Currently tested using [this test suite](https://github.com/parttimenerd/basic-profiler-tests). This runs profiles the [Renaissance](https://renaissance.dev/) benchmark with
> - ... different heap sizes
> - ... different GCs
> - ... different samplers (the standard JFR and the new CPU Time Sampler and both)
> - ... different JFR recording durations
> - ... different chunk-sizes

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

  Move timer_t onto the heap

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/25302/files
  - new: https://git.openjdk.org/jdk/pull/25302/files/e3addfe0..145fe20d

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=25302&range=07
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=25302&range=06-07

  Stats: 40 lines in 3 files changed: 13 ins; 7 del; 20 mod
  Patch: https://git.openjdk.org/jdk/pull/25302.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/25302/head:pull/25302

PR: https://git.openjdk.org/jdk/pull/25302