RFR: 8314653: Metaspace: remove allocation guard feature [v4]

[Thomas Stuefe]

> In Metaspace in debug builds, one can guard allocations. This has been a useful feature in during implementation of JEP 387 to find bugs, but has not found much use thereafter, and remains an obscure and underused feature.
> 
> But these guards cause quite a bit of complexity, mainly since they make testing difficult: with guards on, predicting arena growth gets quite complex.
> 
> I propose to remove this feature to reduce Metaspace complexity.
> 
> Tests: local (mac m1, Linux x64) Metaspace tests. GHAs.

Thomas Stuefe 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 five additional commits since the last revision:

 - copyrights
 - Merge branch 'master' into metaspace-remove-allocation-guard
 - Merge branch 'openjdk:master' into metaspace-remove-allocation-guard
 - Merge branch 'openjdk:master' into metaspace-remove-allocation-guard
 - start

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/19611/files
  - new: https://git.openjdk.org/jdk/pull/19611/files/e9c6d960..6829192a

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=19611&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=19611&range=02-03

  Stats: 4960 lines in 224 files changed: 3413 ins; 684 del; 863 mod
  Patch: https://git.openjdk.org/jdk/pull/19611.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/19611/head:pull/19611

PR: https://git.openjdk.org/jdk/pull/19611