Integrated: Merge lworld

[Vicente Romero]

Merge branch 'lworld' into bworld_merge_lworld

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Commit messages:
 - Merge branch 'lworld' into bworld_merge_lworld
 - Show null restriction markers in javadoc.
 - [bworld] Fix iterating arg types for null checks
 - [bworld] Remove the old NullRestricted attribute
 - Merge lworld
 - [bworld] fixing regression tests
 - [bworld] javac crash for abstract methods with null restricted arguments
 - [bworld] BasicAccessFlags and JavaBaseCheckSince failing
 - JVM detect null checked flag
 - Merge lworld
 - ... and 124 more: https://git.openjdk.org/valhalla/compare/dec1b9e6...47bb6809

The merge commit only contains trivial merges, so no merge-specific webrevs have been generated.

Changes: https://git.openjdk.org/valhalla/pull/2073/files
  Stats: 7555 lines in 118 files changed: 7148 ins; 95 del; 312 mod
  Patch: https://git.openjdk.org/valhalla/pull/2073.diff
  Fetch: git fetch https://git.openjdk.org/valhalla.git pull/2073/head:pull/2073

PR: https://git.openjdk.org/valhalla/pull/2073