RFR: 8377048: Shenandoah: shenandoahLock related improvments [v3]

[Xiaolong Peng]

> While I was working on https://bugs.openjdk.org/browse/JDK-8373371, I made these changes to the shenandoahLock, but I feel it make sense peel off these changes into a separate PR as they are not really related to JDK-8373371. 
> 
> Major thing in this PR is to use template for ShenandoahReentrantLock and ShenandoahLocker so we could get rid of duplicate code, along with some other changes where the locks are used e.g. use type alias for ShenandoahNMethodLock and ShenandoahNMethodLocker, use ShenandoahReentrantLock for ShenandoahRebuildLock.
> 
> Another improvement is to strengthen assert in SheandnoahHeapLocker to avoid potential dead lock(this was also discussed in previous PR [here](https://github.com/openjdk/jdk/pull/27612#discussion_r2479898169) and our internal channel
> 
> ### Test
> - [x] MacOS aach64, server fastdebug: hotspot_gc_shenandoah
> - [x] GHA

Xiaolong Peng has updated the pull request incrementally with one additional commit since the last revision:

  Locker class should assume that lock instance is never be nullptr

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/29543/files
  - new: https://git.openjdk.org/jdk/pull/29543/files/14cbd3ed..af4cbe5c

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=29543&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=29543&range=01-02

  Stats: 12 lines in 3 files changed: 0 ins; 7 del; 5 mod
  Patch: https://git.openjdk.org/jdk/pull/29543.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/29543/head:pull/29543

PR: https://git.openjdk.org/jdk/pull/29543