RFR: 8336299: Improve GCLocker stall diagnostics [v6]

[Neethu Prasad]

> **Notes**
> Adding logs to get more visibility into how fast a thread resumes from allocation stall. 
> 
> **Testing**
> * tier 1, tier 2, hotspot_gc tests.
> 
> Example log messages
> 
> 1. Last thread exiting. Performing GC after exiting critical section. Thread "main" 0 locked.
> 
> 2. Thread exiting critical region Thread "main" 0 locked.
> 
> 3. Thread stalled by JNI critical section. Resumed after 586ms. Thread "Thread-0".
> 
> 4. Thread blocked to enter critical region. Resumed after 1240ms. Thread "SIGINT handler".

Neethu Prasad has updated the pull request incrementally with one additional commit since the last revision:

  address feedback regarding logger potentially getting instantiated multiple times

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/20277/files
  - new: https://git.openjdk.org/jdk/pull/20277/files/77fd9d55..6ca6f29d

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=20277&range=05
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=20277&range=04-05

  Stats: 21 lines in 1 file changed: 5 ins; 6 del; 10 mod
  Patch: https://git.openjdk.org/jdk/pull/20277.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/20277/head:pull/20277

PR: https://git.openjdk.org/jdk/pull/20277