RFR: Merge jdk18

[Jesper Wilhelmsson]

Forwardport JDK 18 -> JDK 19

-------------

Commit messages:
 - Merge remote-tracking branch 'jdk18/master' into Merge_jdk18
 - 8279529: ProblemList java/nio/channels/DatagramChannel/ManySourcesAndTargets.java on macosx-aarch64
 - 8278612: [macos] test/jdk/java/awt/dnd/RemoveDropTargetCrashTest crashes with VoiceOver on macOS
 - 8279525: ProblemList java/awt/GraphicsDevice/CheckDisplayModes.java on macosx-aarch64
 - 8278897: Alignment of heap segments is not enforced correctly
 - 8279222: Incorrect legacyMap.get in java.security.Provider after JDK-8276660
 - 8278948: compiler/vectorapi/reshape/TestVectorCastAVX1.java crashes in assembler

The webrevs contain the adjustments done while merging with regards to each parent branch:
 - master: https://webrevs.openjdk.java.net/?repo=jdk&pr=6975&range=00.0
 - jdk18: https://webrevs.openjdk.java.net/?repo=jdk&pr=6975&range=00.1

Changes: https://git.openjdk.java.net/jdk/pull/6975/files
  Stats: 750 lines in 28 files changed: 687 ins; 8 del; 55 mod
  Patch: https://git.openjdk.java.net/jdk/pull/6975.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/6975/head:pull/6975

PR: https://git.openjdk.java.net/jdk/pull/6975