[jdk21u-dev] RFR: 8331572: Allow using OopMapCache outside of STW GC phases [v3]

[Aleksey Shipilev]

> Unclean backport to improve GC and general stack walk performance when walking interpreted frames.
> 
> This is one of few backports that gets `OopMapCache` behavior similar to mainline. This makes [JDK-8335409](https://bugs.openjdk.org/browse/JDK-8335409) backport easier, because it avoids lots of conflicts, resolving which might introduce surprising bugs. Aligning this code with mainline makes accidents less likely.
> 
> The point of uncleanliness comes from the way we hook up the cleanup notifications to Service Thread. In later JDKs, [JDK-8329488](https://bugs.openjdk.org/browse/JDK-8329488) made Service Thread wake up regularly to do various cleanups. In JDK 21, we still need to hook up the clean up to the "usual" place in safepoint epilog.
> 
> Additional testing:
>  - [x] Linux x86_64 server fastdebug, `all`

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 four additional commits since the last revision:

 - Merge branch 'master' into JDK-8331572-oopmap-cache-all
 - Backport 05ff3185edd25b381a97f6879f496e97b62dddc2
 - Merge branch 'master' into JDK-8331572-oopmap-cache-all
 - Backport d999b81e7110751be402012e1ed41b3256f5895e

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

Changes:
  - all: https://git.openjdk.org/jdk21u-dev/pull/610/files
  - new: https://git.openjdk.org/jdk21u-dev/pull/610/files/9000a426..fc7b61cb

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=610&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=610&range=01-02

  Stats: 31780 lines in 390 files changed: 15974 ins; 13586 del; 2220 mod
  Patch: https://git.openjdk.org/jdk21u-dev/pull/610.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u-dev.git pull/610/head:pull/610

PR: https://git.openjdk.org/jdk21u-dev/pull/610