[lworld] Integrated: 8334294: [lworld] several javac tests are failing in valhalla

[Vicente Romero]

adding @enablePreview to several tests, they are not explicitly using any preview feature but the libs they depend on do use classes like `java.util.Optional` which is a value based class

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Commit messages:
 - 8334294: [lworld] several javac tests are failing in valhalla

Changes: https://git.openjdk.org/valhalla/pull/1130/files
  Webrev: https://webrevs.openjdk.org/?repo=valhalla&pr=1130&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8334294
  Stats: 46 lines in 39 files changed: 39 ins; 5 del; 2 mod
  Patch: https://git.openjdk.org/valhalla/pull/1130.diff
  Fetch: git fetch https://git.openjdk.org/valhalla.git pull/1130/head:pull/1130

PR: https://git.openjdk.org/valhalla/pull/1130