[lworld] RFR: 8328543: [lworld] Library and test updates to use --enable-preview instead of ValhallaFeatures [v4]

[Roger Riggs]

> Update AccessFlag and tests to JEP 401 and use of --enable-preview instead of ValhallaFeatures.
> Minor formatting change to java.lang.Character to allow it to be a value class with --enable-preview.
> (The class file format version numbers will need to be updated when re-synching with the mainline).

Roger Riggs has updated the pull request incrementally with one additional commit since the last revision:

  condition on enable preview

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Changes:
  - all: https://git.openjdk.org/valhalla/pull/1060/files
  - new: https://git.openjdk.org/valhalla/pull/1060/files/6085d5ef..bd5886a1

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=valhalla&pr=1060&range=03
 - incr: https://webrevs.openjdk.org/?repo=valhalla&pr=1060&range=02-03

  Stats: 5 lines in 1 file changed: 3 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/valhalla/pull/1060.diff
  Fetch: git fetch https://git.openjdk.org/valhalla.git pull/1060/head:pull/1060

PR: https://git.openjdk.org/valhalla/pull/1060