[lworld] RFR: 8328543: [lworld] Library and test updates to use --enable-preview instead of ValhallaFeatures [v7]

[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:

  Preview and non-preview tests cannot be supported by a single test due to compilation of value classes.
  Moved preview support for access flags to a new test (ClassAccessFlagPreviewTest) to be run only with --enable-preview.
  Reverted all changes to ClassAccessFlagTest and will only run when not --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/98860d94..c3fb4d85

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=valhalla&pr=1060&range=06
 - incr: https://webrevs.openjdk.org/?repo=valhalla&pr=1060&range=05-06

  Stats: 68 lines in 2 files changed: 8 ins; 42 del; 18 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