RFR: 8331572: Allow using OopMapCache outside of STW GC phases

[Aleksey Shipilev]

As the reproducer in the issue shows, we would also like to use the `OopMapCache` during the concurrent GC phases. Zhengyu mentions there is also a production problem for stack walking that would benefit from letting `OopMapCache` be used without looking at GC at all.

This PR unblocks `OopMapCache` uses for everything. Cleanups are nominally done by service thread. But, still appreciating that majority of use cases would be from GCs, we leave the proactive cleanups from the GC ops here as well. It requires the synchronization between readers that might be copying out the entries out of the hashmap and the concurrent reclamation. Handily, `GlobalCounter` can be used for that purpose. 

After this lands, I think we can go over `OopMapCache::compute_one_oop_map` uses and see if they would instead like to use the cached `lookup` to benefit from this cache too. I think those paths are for OSR and deopts, so their performance is unlikely to be critical. This PR already covers the concurrent GC paths well.

Additional testing:
 - [x] Performance test reproducer from the bug improves significantly
 - [x] Linux AArch64 server fastdebug, `hotspot_gc_shenandoah` (10x)
 - [ ] Linux AArch64 server fastdebug, `all`
 - [x] Linux x86_64 server fastdebug, `all`

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Commit messages:
 - Avoid double handle-izing on GC critical path
 - Move critical section to a closer scope
 - Comments
 - Fix

Changes: https://git.openjdk.org/jdk/pull/19229/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=19229&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8331572
  Stats: 80 lines in 8 files changed: 42 ins; 13 del; 25 mod
  Patch: https://git.openjdk.org/jdk/pull/19229.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/19229/head:pull/19229

PR: https://git.openjdk.org/jdk/pull/19229