RFR: Merge openjdk/jdk21u:master

[William Kemper]

Merges tag jdk-21.0.9+6

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Commit messages:
 - 8360518: Docker tests do not work when asan is configured
 - 8362855: Test java/net/ipv6tests/TcpTest.java should report SkippedException when there no ia4addr  or ia6addr
 - 8350807: Certificates using MD5 algorithm that are disabled by default are incorrectly allowed in TLSv1.3 when re-enabled
 - 8342074: Fix runtime/Thread/TestAlwaysPreTouchStacks.java to be flagless or accept VM flags
 - 8351487: [ubsan] jvmti.h runtime error: load of value which is not a valid value
 - 8352765: G1CollectedHeap::expand_and_allocate() may fail to allocate even after heap expansion succeeds
 - 8338939: Simplify processing of hidden class names
 - 8343607: C2: Shenandoah crashes during barrier expansion in Continuation::enter
 - 8355429: Open source ProgressMonitor test
 - 8354285: Open source Swing tests Batch 3
 - ... and 2 more: https://git.openjdk.org/shenandoah-jdk21u/compare/36910541...48f48ec7

The webrev contains the conflicts with master:
 - merge conflicts: https://webrevs.openjdk.org/?repo=shenandoah-jdk21u&pr=217&range=00.conflicts

Changes: https://git.openjdk.org/shenandoah-jdk21u/pull/217/files
  Stats: 1007 lines in 51 files changed: 712 ins; 204 del; 91 mod
  Patch: https://git.openjdk.org/shenandoah-jdk21u/pull/217.diff
  Fetch: git fetch https://git.openjdk.org/shenandoah-jdk21u.git pull/217/head:pull/217

PR: https://git.openjdk.org/shenandoah-jdk21u/pull/217