RFR: Merge openjdk/jdk21u-dev:master

[William Kemper]

Merges tag jdk-21.0.6+1

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Commit messages:
 - 8342701: [PPC64] TestOSRLotsOfLocals.java crashes
 - 8334560: [PPC64]: postalloc_expand_java_dynamic_call_sched does not copy all fields
 - 8328379: Convert URLDragTest.html applet test to main
 - 8195675: Call to insertText with single character from custom Input Method ignored
 - 8325506: Ensure randomness is only read from provided SecureRandom object
 - 8320673: PageFormat/CustomPaper.java has no Pass/Fail buttons; multiple instructions
 - 8322754: click JComboBox when dialog about to close causes IllegalComponentStateException
 - 8225220: When the Tab Policy is checked,the scroll button direction displayed incorrectly.
 - 8316428: G1: Nmethod count statistics only count last code root set iterated
 - 8333824: Unused ClassValue in VarHandles
 - ... and 123 more: https://git.openjdk.org/shenandoah-jdk21u/compare/dfcd8d2e...7dc0f7a6

The webrev contains the conflicts with master:
 - merge conflicts: https://webrevs.openjdk.org/?repo=shenandoah-jdk21u&pr=134&range=00.conflicts

Changes: https://git.openjdk.org/shenandoah-jdk21u/pull/134/files
  Stats: 15749 lines in 328 files changed: 9595 ins; 5011 del; 1143 mod
  Patch: https://git.openjdk.org/shenandoah-jdk21u/pull/134.diff
  Fetch: git fetch https://git.openjdk.org/shenandoah-jdk21u.git pull/134/head:pull/134

PR: https://git.openjdk.org/shenandoah-jdk21u/pull/134