RFR: 8359110: Log accumulated GC and process CPU time upon VM exit [v15]

[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:

  Fixes after @albertnetymk review

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/25779/files
  - new: https://git.openjdk.org/jdk/pull/25779/files/3104ff6a..08093057

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=25779&range=14
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=25779&range=13-14

  Stats: 6 lines in 2 files changed: 4 ins; 1 del; 1 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