RFR: 8317562: [JFR] Compilation queue statistics [v2]

[Mat Carter]

> Adding a new periodic jfr event to monitor and output statistics for the compiler queues.  You will see one event per compiler queue (c1 and c2)
> 
> Passes tier1 on linux (x86) and mac (aarch64)

Mat Carter has updated the pull request incrementally with one additional commit since the last revision:

  fixed return type and changed NULL to nullptr

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Changes:
  - all: https://git.openjdk.org/jdk/pull/16211/files
  - new: https://git.openjdk.org/jdk/pull/16211/files/6413be5b..6c0b1670

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=16211&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=16211&range=00-01

  Stats: 3 lines in 2 files changed: 0 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/16211.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/16211/head:pull/16211

PR: https://git.openjdk.org/jdk/pull/16211