RFR: Merge lworld [v2]

[Vicente Romero]

> Merge branch 'lworld' into lw5_merge_lworld
> # Conflicts:
> #	test/langtools/tools/javac/diags/examples/ReturnBeforeSuperclassInit.java

Vicente Romero has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 74 commits:

 - Merge branch 'lworld' into lw5_merge_lworld
   
   # Conflicts:
   #	test/langtools/tools/javac/diags/examples/ReturnBeforeSuperclassInit.java
 - Merge lworld
 - Merge lworld
 - 8373670: [lworld] Relax jcheck checks
   
   Reviewed-by: vromero
 - Merge
 - Merge
 - Merge lworld
 - Merge lworld
 - Merge lworld
 - 8347754: [lw5] fix the order of nullness markers in signatures
 - ... and 64 more: https://git.openjdk.org/valhalla/compare/43b6a738...50a5d2ba

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Changes: https://git.openjdk.org/valhalla/pull/1964/files
  Webrev: https://webrevs.openjdk.org/?repo=valhalla&pr=1964&range=01
  Stats: 6804 lines in 102 files changed: 6680 ins; 2 del; 122 mod
  Patch: https://git.openjdk.org/valhalla/pull/1964.diff
  Fetch: git fetch https://git.openjdk.org/valhalla.git pull/1964/head:pull/1964

PR: https://git.openjdk.org/valhalla/pull/1964