RFR: Merge lworld

[Vicente Romero]

Merge branch 'lworld' into bworld_merge_lworld

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Commit messages:
 - Merge branch 'lworld' into bworld_merge_lworld
 - 8376652: [lworld] Explicit and consistent names for nonstatic fields in FieldLayout
 - 8373916: [lworld] TypeName.this.FieldName should be restricted in early construction context
 - 8376791: [lworld] C2 compilation hits assert(!not_flat || !is_flat()) failed: inconsistency
 - 8376813: [lworld] Add print for dummy field reused as null-marker

The webrevs contain the adjustments done while merging with regards to each parent branch:
 - bworld: https://webrevs.openjdk.org/?repo=valhalla&pr=2038&range=00.0
 - lworld: https://webrevs.openjdk.org/?repo=valhalla&pr=2038&range=00.1

Changes: https://git.openjdk.org/valhalla/pull/2038/files
  Stats: 147 lines in 12 files changed: 88 ins; 13 del; 46 mod
  Patch: https://git.openjdk.org/valhalla/pull/2038.diff
  Fetch: git fetch https://git.openjdk.org/valhalla.git pull/2038/head:pull/2038

PR: https://git.openjdk.org/valhalla/pull/2038