RFR: Merge openjdk/jdk:master [v2]

[William Kemper]

> This merges tag jdk-21+20. Please have a look at [this change](https://github.com/openjdk/shenandoah/commit/f9a114efcbfdf5b8b8d605e8b431a9312c3b6111) to resolve conflicts between `CardTable` and `ShenandoahCardTable`.

William Kemper has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 273 commits:

 - Reduce coupling between shenandoah card table and shared card table
 - Merge tag 'jdk-21+20' into merge-jdk-21+20
   
   Added tag jdk-21+20 for changeset 750bece0
 - Remove redundant initialization code
   
   Reviewed-by: shade
 - Usage tracking cleanup
   
   Reviewed-by: kdnilsen, ysr
 - Use state of mark context itself to track stability of old mark bitmap
   
   Reviewed-by: ysr, shade
 - 8306334: Handle preemption of old cycle between filling and bootstrap phases
   
   Reviewed-by: kdnilsen
 - Eliminate TODO in ShenandoahHeuristics::select_aged_regions
   
   Reviewed-by: wkemper
 - Add unique ticket number for each disabled test
   
   Reviewed-by: ysr, shade
 - Specialize ShenandoahGenerationType to avoid generational check penalty on fast paths
   
   Reviewed-by: kdnilsen, wkemper
 - Account for humongous object waste
   
   Reviewed-by: ysr, kdnilsen
 - ... and 263 more: https://git.openjdk.org/shenandoah/compare/750bece0...f9a114ef

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Changes: https://git.openjdk.org/shenandoah/pull/269/files
 Webrev: https://webrevs.openjdk.org/?repo=shenandoah&pr=269&range=01
  Stats: 18852 lines in 215 files changed: 17207 ins; 794 del; 851 mod
  Patch: https://git.openjdk.org/shenandoah/pull/269.diff
  Fetch: git fetch https://git.openjdk.org/shenandoah.git pull/269/head:pull/269

PR: https://git.openjdk.org/shenandoah/pull/269