RFR: 8359110: Log accumulated GC and process CPU time upon VM exit [v10]

[Jonas Norlinder]

> Add support to log CPU cost for GC during VM exit with `-Xlog:gc`.
> 
> 
> [1.500s][info ][gc] GC CPU cost: 1.75%
> 
> 
> Additionally, detailed information may be retrieved with `-Xlog:gc=trace`
> 
> 
> [1.500s][trace][gc] Process CPU time: 4.945370s
> [1.500s][trace][gc] GC CPU time: 0.086382s
> [1.500s][info ][gc] GC CPU cost: 1.75%

Jonas Norlinder has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 18 commits:

 - Merge branch 'master' of github.com:JonasNorlinder/openjdk_jdk into gc_cpu_time
 - Implement CollectedHeap::before_exit() as suggested by @stefank
 - Remove incorrect is_gc_operation call after rebase
 - More clean up, remove virtual
 - Fixes after feedback from @stefank
 - Remove extra whitespace
 - operation_is_gc -> is_gc_operation per @stefank suggestion
 - Only sample if needed
 - Remove explicit super call and minor fixes
 - Add CPU time tracking for string deduplication to log_gc_vtime
 - ... and 8 more: https://git.openjdk.org/jdk/compare/aa191119...0993931f

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Changes: https://git.openjdk.org/jdk/pull/25779/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=25779&range=09
  Stats: 265 lines in 17 files changed: 253 ins; 7 del; 5 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