RFR: 8315149: Add hsperf counters for CPU time of internal GC threads [v19]

[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 dholmes@ comments

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Changes:
  - all: https://git.openjdk.org/jdk/pull/15082/files
  - new: https://git.openjdk.org/jdk/pull/15082/files/7e1812e3..0a2565dc

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=15082&range=18
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=15082&range=17-18

  Stats: 7 lines in 5 files changed: 1 ins; 2 del; 4 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