[lworld] RFR: 8371915: [lworld] LayoutKind enum should have helper methods

[Frederic Parain]

Add some helper methods to test properties of layouts in a more reliable way.

Tested with Mach5, tier 1 to 3.

Fred

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Commit messages:
 - Add helper methods to LayoutKind

Changes: https://git.openjdk.org/valhalla/pull/1745/files
  Webrev: https://webrevs.openjdk.org/?repo=valhalla&pr=1745&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8371915
  Stats: 98 lines in 11 files changed: 35 ins; 43 del; 20 mod
  Patch: https://git.openjdk.org/valhalla/pull/1745.diff
  Fetch: git fetch https://git.openjdk.org/valhalla.git pull/1745/head:pull/1745

PR: https://git.openjdk.org/valhalla/pull/1745