[jdk21u-dev] RFR: 8350313: Include timings for leaving safepoint in safepoint logging

[Xiaolong Peng]

Hi all,

This pull request contains a backport of commit [9ec46968](https://github.com/openjdk/jdk/commit/9ec46968fbfddf99a8349cb6903d24b1c2fdaf1d) from the [openjdk/jdk](https://git.openjdk.org/jdk) repository.

It is not a clean backport, because in JDK21 safepoint log contains cleanup time, which has been removed as a result of the change to move OopStorage code from safepoint cleanup([link](https://github.com/openjdk/jdk/commit/3e9c3811669196945d7227affc28728670a256c5#diff-d61020d12394708828d066d097d823180c01b74d35d4c3e369aead062abc11ef))

Here is some samples of safepoint logs  on JDK21 with this backport:

[0.373s][info][safepoint] Safepoint "ICBufferFull", Time since last: 328087237 ns, Reaching safepoint: 76807 ns, Cleanup: 85286 ns, At safepoint: 968 ns, Leaving safepoint: 6828 ns, Total: 169889 ns
[1.023s][info][safepoint] Safepoint "ICBufferFull", Time since last: 649442642 ns, Reaching safepoint: 9755 ns, Cleanup: 110653 ns, At safepoint: 819 ns, Leaving safepoint: 2384 ns, Total: 123611 ns
[1.178s][info][safepoint] Safepoint "ICBufferFull", Time since last: 155146184 ns, Reaching safepoint: 79728 ns, Cleanup: 100436 ns, At safepoint: 1010 ns, Leaving safepoint: 12941 ns, Total: 194115 ns
[1.356s][info][safepoint] Safepoint "ICBufferFull", Time since last: 177647363 ns, Reaching safepoint: 7169 ns, Cleanup: 94057 ns, At safepoint: 690 ns, Leaving safepoint: 1773 ns, Total: 103689 ns
[2.653s][info][safepoint] Safepoint "Cleanup", Time since last: 1000091335 ns, Reaching safepoint: 296258038 ns, Cleanup: 41829 ns, At safepoint: 1529 ns, Leaving safepoint: 120670 ns, Total: 296422066 ns


### Test
- [x] Tier 1
- [x] Tier 2
- [x] Manual test with safepoint log enabled and verification of safepoint logs 

Thanks!

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

Commit messages:
 - 8350313: Include timings for leaving safepoint in safepoint logging

Changes: https://git.openjdk.org/jdk21u-dev/pull/1683/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=1683&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8350313
  Stats: 12 lines in 2 files changed: 11 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk21u-dev/pull/1683.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u-dev.git pull/1683/head:pull/1683

PR: https://git.openjdk.org/jdk21u-dev/pull/1683