[lworld] RFR: 8373706: [lworld] Layout names should be self-explanatory

[Frederic Parain]

Renaming of layout kinds to make them self-explanatory.
Also, provides layout kind -> string methods to normalize names of layouts in all logging messages and tests.

Initially tested with tier 1-3 (re-validating after merge/minor changes).

Thank you.

Fred

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Commit messages:
 - Make layout names should be self-explanatory

Changes: https://git.openjdk.org/valhalla/pull/1801/files
  Webrev: https://webrevs.openjdk.org/?repo=valhalla&pr=1801&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8373706
  Stats: 162 lines in 15 files changed: 57 ins; 17 del; 88 mod
  Patch: https://git.openjdk.org/valhalla/pull/1801.diff
  Fetch: git fetch https://git.openjdk.org/valhalla.git pull/1801/head:pull/1801

PR: https://git.openjdk.org/valhalla/pull/1801