Integrated: Merge lworld

[Vicente Romero]

Merge branch 'lworld' into lw5
# Conflicts:
#	src/jdk.compiler/share/classes/com/sun/tools/javac/code/Flags.java
#	src/jdk.compiler/share/classes/com/sun/tools/javac/comp/Check.java

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Commit messages:
 - Merge branch 'lworld' into lw5_merge_lworld
 - Merge lworld
 - 8340125: [lw5] null checks are not being generated for method invocations and array writes
 - Merge lworld
 - 8340027: [lw5] the ACC_STRICT flag is not being set for non-nullable static fields
 - Merge lworld
 - 8339357: [lw5] make non-nullable instance fields strict
 - 8339339: [lw5] javac should issue an error if a null-restricted field is left uninitialized, fix override related warnings
 - 8338910: [lw5] enhance the Signature attribute to represent nullability
 - Improve support for nullable types and arrays
 - ... and 51 more: https://git.openjdk.org/valhalla/compare/fa2c4ff7...46161ee6

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

Changes: https://git.openjdk.org/valhalla/pull/1301/files
  Stats: 6860 lines in 106 files changed: 6739 ins; 5 del; 116 mod
  Patch: https://git.openjdk.org/valhalla/pull/1301.diff
  Fetch: git fetch https://git.openjdk.org/valhalla.git pull/1301/head:pull/1301

PR: https://git.openjdk.org/valhalla/pull/1301