[lworld] RFR: 8372619: [lworld] Use Character caches in --enable-preview

[Roger Riggs]

Re-enable Character.cache with or without --enable-preview.
A more complete removal of the Character cache needs some Hotspot changes.

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Commit messages:
 - 8372619: [lworld] Use Character caches in --enable-preview

Changes: https://git.openjdk.org/valhalla/pull/1763/files
  Webrev: https://webrevs.openjdk.org/?repo=valhalla&pr=1763&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8372619
  Stats: 4 lines in 1 file changed: 0 ins; 2 del; 2 mod
  Patch: https://git.openjdk.org/valhalla/pull/1763.diff
  Fetch: git fetch https://git.openjdk.org/valhalla.git pull/1763/head:pull/1763

PR: https://git.openjdk.org/valhalla/pull/1763