RFR: Merge lworld

[Vicente Romero]

Merge branch 'lworld' into jep_401_javac_merge_lworld

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Commit messages:
 - Merge branch 'lworld' into jep_401_javac_merge_lworld
 - Merge jdk
 - 8317510: Change Windows debug symbol files naming to avoid losing info when an executable and a library share the same name
 - 8318613: ChoiceFormat patterns are not well tested
 - 8318186: ChoiceFormat inconsistency between applyPattern() and setChoices()
 - 8318487: Specification of the ListFormat.equals() method can be improved
 - 8317360: Missing null checks in JfrCheckpointManager and JfrStringPool initialization routines
 - 8318735: RISC-V: Enable related hotspot tests run on riscv
 - 8318727: Enable parallelism in vmTestbase/vm/gc/concurrent tests
 - 8318607: Enable parallelism in vmTestbase/nsk/stress/jni tests
 - ... and 116 more: https://git.openjdk.org/valhalla/compare/969c4b7c...7a973fce

The webrevs contain the adjustments done while merging with regards to each parent branch:
 - jep_401_javac: https://webrevs.openjdk.org/?repo=valhalla&pr=985&range=00.0
 - lworld: https://webrevs.openjdk.org/?repo=valhalla&pr=985&range=00.1

Changes: https://git.openjdk.org/valhalla/pull/985/files
  Stats: 13971 lines in 451 files changed: 8742 ins; 3026 del; 2203 mod
  Patch: https://git.openjdk.org/valhalla/pull/985.diff
  Fetch: git fetch https://git.openjdk.org/valhalla.git pull/985/head:pull/985

PR: https://git.openjdk.org/valhalla/pull/985