RFR: Merge jdk

[Mikael Vidstedt]

Merge in jdk-16+32

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Commit messages:
 - Merge jdk
 - 8259063: Possible deadlock with vtable/itable creation vs concurrent class unloading
 - 8259657: typo in generated HELP page prevents localization
 - 8258272: LoadVectorMaskedNode can't be replaced by zero con
 - 8259560: Zero m68k: "static assertion failed: align" after JDK-8252049
 - 8258985: Parallel WeakProcessor may use too few threads
 - 8259061: C2: assert(found) failed: memory-writing node is not placed in its original loop or an ancestor of it
 - 8259601: AArch64: Fix reinterpretX2D match rule issue
 - 8259275: JRuby crashes while resolving invokedynamic instruction
 - 8259353: VectorReinterpretNode is incorrectly optimized out
 - ... and 96 more: https://git.openjdk.java.net/portola/compare/d865bc02...0f98e7d8

The webrevs contain the adjustments done while merging with regards to each parent branch:
 - jdk16: https://webrevs.openjdk.java.net/?repo=portola&pr=20&range=00.0
 - jdk: https://webrevs.openjdk.java.net/?repo=portola&pr=20&range=00.1

Changes: https://git.openjdk.java.net/portola/pull/20/files
  Stats: 9043 lines in 353 files changed: 5033 ins; 3015 del; 995 mod
  Patch: https://git.openjdk.java.net/portola/pull/20.diff
  Fetch: git fetch https://git.openjdk.java.net/portola pull/20/head:pull/20

PR: https://git.openjdk.java.net/portola/pull/20