RFR: 8372704: ThreadMXBean.getThreadUserTime may return total time [v2]

[Jonas Norlinder]

> getThreadUserTime will return total (system + user) time if called with e.g. ManagementFactory.getThreadMXBean().getThreadUserTime(Thread.currentThread().threadId()).
> 
> The specification for this methods states that only user-level CPU time would ever be returned on success.

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

  Fix copyright year

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Changes:
  - all: https://git.openjdk.org/jdk/pull/28545/files
  - new: https://git.openjdk.org/jdk/pull/28545/files/4fdfbaf6..3d541253

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=28545&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=28545&range=00-01

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/28545.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/28545/head:pull/28545

PR: https://git.openjdk.org/jdk/pull/28545