RFR: Merge openjdk/jdk21u:master

[William Kemper]

Merges tag jdk-21.0.9+5

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Commit messages:
 - 8353748: Open source several swing tests batch6
 - 8340547: Starting many threads can delay safepoints
 - 8361478: GHA: Use MSYS2 from GHA runners
 - 8353293: Open source several swing tests batch4
 - 8358004: Delete applications/scimark/Scimark.java test
 - 8353000: Open source several swing tests batch2
 - 8353213: Open source several swing tests batch3
 - 8279005: sun/tools/jstat tests do not check for test case exit codes after JDK-8245129
 - 8365811: test/jdk/java/net/CookieHandler/B6644726.java failure - "Should have 5 cookies. Got only 4, expires probably didn't parse correctly"
 - 8361328: cds/appcds/dynamicArchive/TestAutoCreateSharedArchive.java archive timestamps comparison failed
 - ... and 34 more: https://git.openjdk.org/shenandoah-jdk21u/compare/d90297a8...36910541

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

Changes: https://git.openjdk.org/shenandoah-jdk21u/pull/216/files
  Stats: 6815 lines in 128 files changed: 5599 ins; 987 del; 229 mod
  Patch: https://git.openjdk.org/shenandoah-jdk21u/pull/216.diff
  Fetch: git fetch https://git.openjdk.org/shenandoah-jdk21u.git pull/216/head:pull/216

PR: https://git.openjdk.org/shenandoah-jdk21u/pull/216