[lworld] RFR: 8353746: [lworld] Remove the default value and @ImplictlyConstructible annotation

[Frederic Parain]

Removal of the all-zero default value and the @ImplicitlyConstructible annotation.

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Commit messages:
 - Merge branch 'strict_nr' of https://github.com/fparain/valhalla into strict_nr
 - Merge branch 'strict_nr' of github.com:fparain/valhalla into strict_nr
 - Comment adjustment
 - Remove the @ImplicitlyConstructible annotation
 - Update AppCDS tests
 - Merge remote-tracking branch 'upstream/lworld' into strict_nr
 - Fix comment
 - More refactoring
 - Removed null checks for null-free, non-flat fields from C2. More refactoring.
 - More refactoring
 - ... and 12 more: https://git.openjdk.org/valhalla/compare/f662357d...107478ea

Changes: https://git.openjdk.org/valhalla/pull/1389/files
  Webrev: https://webrevs.openjdk.org/?repo=valhalla&pr=1389&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8353746
  Stats: 4168 lines in 183 files changed: 1230 ins; 1553 del; 1385 mod
  Patch: https://git.openjdk.org/valhalla/pull/1389.diff
  Fetch: git fetch https://git.openjdk.org/valhalla.git pull/1389/head:pull/1389

PR: https://git.openjdk.org/valhalla/pull/1389