RFR: Merge jdk20

[Jesper Wilhelmsson]

Forwardport JDK 20 -> JDK 21

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Commit messages:
 - Merge remote-tracking branch 'jdk20/master' into Merge_jdk20
 - 8299123: [BACKOUT] 4512626 Non-editable JTextArea provides no visual indication of keyboard focus
 - 8298162: Test PrintClasses hits assert when run with code that retransform classes
 - 8298061: vmTestbase/nsk/sysdict/vm/stress/btree/btree012/btree012.java failed with "fatal error: refcount has gone to zero"
 - 8298968: G1: Incorrect merged remset stats

The webrevs contain the adjustments done while merging with regards to each parent branch:
 - master: https://webrevs.openjdk.org/?repo=jdk&pr=11744&range=00.0
 - jdk20: https://webrevs.openjdk.org/?repo=jdk&pr=11744&range=00.1

Changes: https://git.openjdk.org/jdk/pull/11744/files
  Stats: 258 lines in 8 files changed: 75 ins; 61 del; 122 mod
  Patch: https://git.openjdk.org/jdk/pull/11744.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/11744/head:pull/11744

PR: https://git.openjdk.org/jdk/pull/11744