RFR: 8277090 : jsr166 refresh for jdk19

[Doug Lea]

This is the jsr166 refresh for jdk19. See https://bugs.openjdk.java.net/browse/JDK-8285450 and https://bugs.openjdk.java.net/browse/JDK-8277090

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Commit messages:
 - whitespace
 - sync with loom
 - 8276202: LogFileOutput.invalid_file_vm asserts when being executed from a read only working directory
 - 8284981: Support the vectorization of some counting-down loops in SLP
 - 8284992: Fix misleading Vector API doc for LSHR operator
 - 8254759: [TEST_BUG] [macosx] javax/swing/JInternalFrame/4202966/IntFrameCoord.html fails
 - 8285945: [BACKOUT] JDK-8285802 AArch64: Consistently handle offsets in MacroAssembler as 64-bit quantities
 - 8284331: Add sanity check for signal handler modification warning.
 - 8285773: Replace Algorithms.eatMemory(...) with WB.fullGC() in vmTestbase/gc/gctests/ReferencesGC/ReferencesGC.java
 - 8284883: JVM crash: guarantee(sect->end() <= sect->limit()) failed: sanity on AVX512
 - ... and 6 more: https://git.openjdk.java.net/jdk/compare/3d07b3c7...501a21e8

Changes: https://git.openjdk.java.net/jdk/pull/8490/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=8490&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8277090
  Stats: 3750 lines in 30 files changed: 2060 ins; 656 del; 1034 mod
  Patch: https://git.openjdk.java.net/jdk/pull/8490.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/8490/head:pull/8490

PR: https://git.openjdk.java.net/jdk/pull/8490