RFR: 8313202: MutexLocker should disallow null Mutexes [v6]

[Aleksey Shipilev]

> As seen in [JDK-8313081](https://bugs.openjdk.org/browse/JDK-8313081), it is fairly easy to pass nullptr `Mutex` to `MutexLocker` by accident, which would just silently avoid the lock.
> 
> There are a few places in Hotspot where we pass `nullptr` to simulate re-entrancy and/or conditionally take the lock. Those places can be more explicit, and the default `MutexLocker` can disallow nullptrs for extra safety.
> 
> More thorough testing with different GC/JIT combinations is running now, we might find more issues there. Meanwhile, please comment on the approach.
> 
> Additional testing:
>  - [x] `grep -R "MutexLocker " src/hotspot | grep -i null`, only new `ConditionalMutexLocker` hits
>  - [x] `grep -R "MutexLocker " src/hotspot | grep -i ?`, no hits
>  - [x] Linux AArch64 fastdebug, `tier1 tier2 tier3` x `Serial Parallel G1 Shenandoah`

Aleksey Shipilev has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains 10 additional commits since the last revision:

 - Merge branch 'master' into JDK-8313202-mutexlocker-nulls
 - Merge branch 'master' into JDK-8313202-mutexlocker-nulls
 - Merge branch 'master' into JDK-8313202-mutexlocker-nulls
 - Merge branch 'master' into JDK-8313202-mutexlocker-nulls
 - Accept one more potentially nullptr mutex
 - Merge branch 'master' into JDK-8313202-mutexlocker-nulls
 - Replace ReentrantMutexLocker with ConditionalMutexLocker
 - Workaround for JDK-8313210
 - Fixing CodeCache analytics
 - Initial work

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/15043/files
  - new: https://git.openjdk.org/jdk/pull/15043/files/7a11505f..8dc9cde7

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=15043&range=05
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=15043&range=04-05

  Stats: 13700 lines in 325 files changed: 9233 ins; 2313 del; 2154 mod
  Patch: https://git.openjdk.org/jdk/pull/15043.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/15043/head:pull/15043

PR: https://git.openjdk.org/jdk/pull/15043