RFR: 8314653: Metaspace: remove allocation guard feature

[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.

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Commit messages:
 - start

Changes: https://git.openjdk.org/jdk/pull/19611/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=19611&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8314653
  Stats: 252 lines in 15 files changed: 0 ins; 242 del; 10 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