RFR: Merge openjdk/jdk21u-dev:master

[William Kemper]

Merges tag jdk-21.0.4+6

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Commit messages:
 - 8334441: Mark tests in jdk_security_infra group as manual

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

Changes: https://git.openjdk.org/shenandoah-jdk21u/pull/61/files
  Stats: 156 lines in 8 files changed: 5 ins; 0 del; 151 mod
  Patch: https://git.openjdk.org/shenandoah-jdk21u/pull/61.diff
  Fetch: git fetch https://git.openjdk.org/shenandoah-jdk21u.git pull/61/head:pull/61

PR: https://git.openjdk.org/shenandoah-jdk21u/pull/61