RFR: 8315149: Add hsperf counters for CPU time of internal GC threads [v18]

[Jonathan Joo]

> 8315149: Add hsperf counters for CPU time of internal GC threads

Jonathan Joo has updated the pull request incrementally with one additional commit since the last revision:

  Clean up test and improve total counter name

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/15082/files
  - new: https://git.openjdk.org/jdk/pull/15082/files/4e51426b..7e1812e3

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=15082&range=17
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=15082&range=16-17

  Stats: 8 lines in 2 files changed: 2 ins; 0 del; 6 mod
  Patch: https://git.openjdk.org/jdk/pull/15082.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/15082/head:pull/15082

PR: https://git.openjdk.org/jdk/pull/15082