RFR: Merge openjdk/jdk21u:master

[William Kemper]

Merges tag jdk-21.0.8+4

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Commit messages:
 - 8297692: Avoid sending per-region GCPhaseParallel JFR events in G1ScanCollectionSetRegionClosure
 - 8352908: Open source several swing tests batch1
 - 8353475: Open source two Swing DefaultCaret tests
 - 8352684: Opensource JInternalFrame tests - series1
 - 8353320: Open source more Swing text tests
 - 8352680: Opensource few misc swing tests
 - 8352676: Opensource JMenu tests - series1
 - 8350383: Test: add more test case for string compare (UL case)
 - 8345547: test/jdk/javax/swing/text/DefaultEditorKit/4278839/bug4278839.java fails in ubuntu22.04
 - 8345447: test/jdk/javax/swing/JToolBar/4529206/bug4529206.java fails in ubuntu22.04
 - ... and 21 more: https://git.openjdk.org/shenandoah-jdk21u/compare/38a356d3...a1e58917

The merge commit only contains trivial merges, so no merge-specific webrevs have been generated.

Changes: https://git.openjdk.org/shenandoah-jdk21u/pull/195/files
  Stats: 12088 lines in 819 files changed: 2987 ins; 162 del; 8939 mod
  Patch: https://git.openjdk.org/shenandoah-jdk21u/pull/195.diff
  Fetch: git fetch https://git.openjdk.org/shenandoah-jdk21u.git pull/195/head:pull/195

PR: https://git.openjdk.org/shenandoah-jdk21u/pull/195