RFR: 8331691: Generational ZGC: Use ZLocker uniformly [v2]

[Guoxiong Li]

> Hi all,
> 
> This patch removes the classes `ZDriverLocker` and `ZDriverUnlocker`, and uses `ZLocker` and newly added `ZUnlocker` instead. Thanks for taking the time to review.
> 
> Testing:
> - [ ] linux-x64-slowdebug test-hotspot_gc
> 
> Best Regards,
> -- Guoxiong

Guoxiong Li has updated the pull request incrementally with one additional commit since the last revision:

  Fix ZUnlocker

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/19092/files
  - new: https://git.openjdk.org/jdk/pull/19092/files/8f8c3491..460718cd

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=19092&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=19092&range=00-01

  Stats: 2 lines in 1 file changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/19092.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/19092/head:pull/19092

PR: https://git.openjdk.org/jdk/pull/19092