RFR: 8359110: Log accumulated GC and process CPU time upon VM exit [v18]

[Jonas Norlinder]

> Add support to log CPU cost for GC during VM exit with `-Xlog:gc+cpu`.
> 
> 
> [2,430s][info][gc,cpu] GC CPU usage: 22,87% (Process: 26,8926s GC: 6,1491s)

Jonas Norlinder has updated the pull request incrementally with one additional commit since the last revision:

  CPUTimeScope->VMThreadCPUTimeScope, remove volatile and reorder elapsed_gc_cpu_time

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Changes:
  - all: https://git.openjdk.org/jdk/pull/25779/files
  - new: https://git.openjdk.org/jdk/pull/25779/files/f9c3aa64..5694d6f3

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=25779&range=17
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=25779&range=16-17

  Stats: 102 lines in 6 files changed: 47 ins; 46 del; 9 mod
  Patch: https://git.openjdk.org/jdk/pull/25779.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/25779/head:pull/25779

PR: https://git.openjdk.org/jdk/pull/25779