[lworld] RFR: 8375740: [lworld] javap prints "value class" while class flags indicate ACC_IDENTITY

[Chen Liang]

Seems like an oversight where "value" is added unconditionally. I changed the behavior to add "identity" for preview identity classes, which was never printed before (because identity is not a source modifier)

Testing: langtools/tools/javap + javac

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Commit messages:
 - 8375740: [lworld] javap prints "value class" while class flags indicate ACC_IDENTITY

Changes: https://git.openjdk.org/valhalla/pull/1938/files
  Webrev: https://webrevs.openjdk.org/?repo=valhalla&pr=1938&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8375740
  Stats: 47 lines in 2 files changed: 36 ins; 0 del; 11 mod
  Patch: https://git.openjdk.org/valhalla/pull/1938.diff
  Fetch: git fetch https://git.openjdk.org/valhalla.git pull/1938/head:pull/1938

PR: https://git.openjdk.org/valhalla/pull/1938