RFR: Merge openjdk/jdk:master

[William Kemper]

Merges tag jdk-21+10.

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Commit messages:
 - Replace NULL with nullptr in generational mode changes
 - Merge jdk-21+10
 - 8302163: Speed up various String comparison methods with ArraysSupport.mismatch
 - 8301460: Clean up LambdaForm to reference BasicType enums directly
 - 8302127: Remove unused arg in write_ref_field_post
 - 8301225: Replace NULL with nullptr in share/gc/shenandoah/
 - 8301700: Increase the default TLS Diffie-Hellman group size from 1024-bit to 2048-bit
 - 8301463: Code in DatagramSocket still refers to resolved JDK-8237352
 - 8302325: Wrong comment in java.base/share/native/libjimage/imageFile.hpp
 - 8300808: Accelerate Base64 on x86 for AVX2
 - ... and 96 more: https://git.openjdk.org/shenandoah/compare/0dbacdfe...0dd53585

The webrevs contain the adjustments done while merging with regards to each parent branch:
 - master: https://webrevs.openjdk.org/?repo=shenandoah&pr=219&range=00.0
 - openjdk/jdk:master: https://webrevs.openjdk.org/?repo=shenandoah&pr=219&range=00.1

Changes: https://git.openjdk.org/shenandoah/pull/219/files
  Stats: 45222 lines in 951 files changed: 16760 ins; 14148 del; 14314 mod
  Patch: https://git.openjdk.org/shenandoah/pull/219.diff
  Fetch: git fetch https://git.openjdk.org/shenandoah pull/219/head:pull/219

PR: https://git.openjdk.org/shenandoah/pull/219