[jdk21u-dev] RFR: 8272364: Parallel GC adaptive size policy may shrink the heap below MinHeapSize

[Daniel Hu]

Clean backports. Fixes miscalculation of Parallal GC ergonomics; followup backports to fix related gtest (JDK-8333674 is trivial and backported so that JDK-8331675 is clean). New test passes with change, fails without. Changes pass GHA and internal Amazon pipelines: jtreg tier1-4 and tck tests on platforms linux x64, aarch64, aarch32; alpine x64, aarch64; mac aarch64, x64; windows x64.

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Commit messages:
 - Merge branch 'openjdk:master' into 8272364
 - Backport a4b49253e34bd0e5d7b7140289275a3311907472
 - Backport 9b436d048ec92f74ec6812ae20fde21751927d4b
 - Backport 6bef0474c8b8773d0d20c0f25c36a2ce9cdbd7e8

Changes: https://git.openjdk.org/jdk21u-dev/pull/2419/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=2419&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8272364
  Stats: 109 lines in 3 files changed: 100 ins; 9 del; 0 mod
  Patch: https://git.openjdk.org/jdk21u-dev/pull/2419.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u-dev.git pull/2419/head:pull/2419

PR: https://git.openjdk.org/jdk21u-dev/pull/2419