RFR: 8315149: Add hsperf counters for CPU time of internal GC threads [v4]

[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:

  address partial comments from Volker and Man

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Changes:
  - all: https://git.openjdk.org/jdk/pull/15082/files
  - new: https://git.openjdk.org/jdk/pull/15082/files/eb911ee1..74b6db2d

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=15082&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=15082&range=02-03

  Stats: 47 lines in 15 files changed: 11 ins; 6 del; 30 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