RFR: Merge openjdk/jdk21u:master [v2]

[William Kemper]

> Merge tip of jdk21u

William Kemper has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains two additional commits since the last revision:

 - Merge 'openjdk-21u/master' into 'shenandoah-jdk21u/master'
 - 8320913: GenShen: Bootstrap 21u backports repo
   
   Reviewed-by: ysr, kdnilsen

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Changes:
  - all: https://git.openjdk.org/shenandoah-jdk21u/pull/2/files
  - new: https://git.openjdk.org/shenandoah-jdk21u/pull/2/files/7c145a52..7c145a52

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=shenandoah-jdk21u&pr=2&range=01
 - incr: https://webrevs.openjdk.org/?repo=shenandoah-jdk21u&pr=2&range=00-01

  Stats: 0 lines in 0 files changed: 0 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/shenandoah-jdk21u/pull/2.diff
  Fetch: git fetch https://git.openjdk.org/shenandoah-jdk21u.git pull/2/head:pull/2

PR: https://git.openjdk.org/shenandoah-jdk21u/pull/2