RFR: 8366035: Simplify CPUTimeCounters::publish_gc_total_cpu_time [v2]

[Guanqiang Han]

> This change refactors CPUTimeCounters::publish_gc_total_cpu_time() to use Atomic::xchg instead of a CAS (cmpxchg) loop.
> Please review it. Thanks

Guanqiang Han has updated the pull request incrementally with one additional commit since the last revision:

  Update cpuTimeCounters.cpp
  
  a small fix

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/26921/files
  - new: https://git.openjdk.org/jdk/pull/26921/files/0b66b63c..6dd9ff83

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=26921&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=26921&range=00-01

  Stats: 2 lines in 1 file changed: 1 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/26921.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/26921/head:pull/26921

PR: https://git.openjdk.org/jdk/pull/26921