Integrated: Merge lworld

[Vicente Romero]

Merge branch 'lworld' into lw5_merge_lworld
# Conflicts:
#	src/jdk.compiler/share/classes/com/sun/tools/javac/code/Preview.java
#	src/jdk.compiler/share/classes/com/sun/tools/javac/code/Source.java
#	src/jdk.compiler/share/classes/com/sun/tools/javac/code/Symtab.java
#	src/jdk.compiler/share/classes/com/sun/tools/javac/comp/Check.java
#	src/jdk.compiler/share/classes/com/sun/tools/javac/comp/Flow.java
#	src/jdk.compiler/share/classes/com/sun/tools/javac/comp/TypeEnter.java
#	src/jdk.compiler/share/classes/com/sun/tools/javac/util/Names.java

-------------

Commit messages:
 - Merge branch 'lworld' into lw5_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
 - 8339087: [lw5] remove parametric types related warnings
 - Add option to disable parametric nullness by default
 - Add inference support for nullable types
 - ... and 48 more: https://git.openjdk.org/valhalla/compare/2c876c9c...05858131

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

Changes: https://git.openjdk.org/valhalla/pull/1259/files
  Stats: 6584 lines in 105 files changed: 6473 ins; 10 del; 101 mod
  Patch: https://git.openjdk.org/valhalla/pull/1259.diff
  Fetch: git fetch https://git.openjdk.org/valhalla.git pull/1259/head:pull/1259

PR: https://git.openjdk.org/valhalla/pull/1259