[lworld] RFR: Early larval frame should be toggled by preview

[Chen Liang]

Early larval frame should be generated by the value classes preview settings. To prevent strict presence without early larvals, add a preview check to block strict without value objects preview enabled.

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Commit messages:
 - Early larval frame should be toggled by preview

Changes: https://git.openjdk.org/valhalla/pull/1637/files
  Webrev: https://webrevs.openjdk.org/?repo=valhalla&pr=1637&range=00
  Stats: 12 lines in 5 files changed: 4 ins; 4 del; 4 mod
  Patch: https://git.openjdk.org/valhalla/pull/1637.diff
  Fetch: git fetch https://git.openjdk.org/valhalla.git pull/1637/head:pull/1637

PR: https://git.openjdk.org/valhalla/pull/1637