RFR: 8315149: Add hsperf counters for CPU time of internal GC threads [v27]

[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:

  add comment and change if defined to ifdef

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/15082/files
  - new: https://git.openjdk.org/jdk/pull/15082/files/2807c191..590df03b

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=15082&range=26
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=15082&range=25-26

  Stats: 4 lines in 1 file changed: 3 ins; 0 del; 1 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