RFR: Merge openjdk/jdk:master

[William Kemper]

Merges jdk-21+18

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Commit messages:
 - Merge tag 'jdk-21+18' into merge-jdk-21-18
 - 8305524: AArch64: Fix arraycopy issue on SVE caused by matching rule vmask_gen_sub
 - 8305203: Simplify trimming operation in Region::Ideal
 - 8300912: Update java/nio/MappedByteBuffer/PmemTest.java to run on x86_64 only
 - 8305484: Compiler::init_c1_runtime unnecessarily uses an Arena that lives for the lifetime of the process
 - 8305809: (fs) Review obsolete Linux kernel dependency on os.version (Unix kernel 2.6.39)
 - 8294806: jpackaged-app ignores splash screen from jar file
 - 8305368: G1 remset chunk claiming may use relaxed memory ordering
 - 8305370: Inconsistent use of for_young_only_phase parameter in G1 predictions
 - 8305663: Wrong iteration order of pause array in g1MMUTracker
 - ... and 47 more: https://git.openjdk.org/shenandoah/compare/b2623500...55440abd

The webrevs contain the adjustments done while merging with regards to each parent branch:
 - master: https://webrevs.openjdk.org/?repo=shenandoah&pr=257&range=00.0
 - openjdk/jdk:master: https://webrevs.openjdk.org/?repo=shenandoah&pr=257&range=00.1

Changes: https://git.openjdk.org/shenandoah/pull/257/files
  Stats: 14965 lines in 486 files changed: 7514 ins; 6258 del; 1193 mod
  Patch: https://git.openjdk.org/shenandoah/pull/257.diff
  Fetch: git fetch https://git.openjdk.org/shenandoah.git pull/257/head:pull/257

PR: https://git.openjdk.org/shenandoah/pull/257