[lworld] RFR: 8377327: [lworld] SA tests fail with --enable-preview

[Coleen Phillimore]

This set of SA tests fail because SA tries to parse field layouts.  With Valhalla there is new field info in the field stream, which is used when --enable-preview is used since some fields are flattened.  This adds minimal support for that.

Tested with tier1-4.

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Commit messages:
 - Revert FieldType change.  Was caused by the FieldInfo stream parsing errors.
 - Don't use 'V' for FieldType.first.  Fix a rogue Q.
 - 8377327: [lworld] SA tests fail with --enable-preview

Changes: https://git.openjdk.org/valhalla/pull/2064/files
  Webrev: https://webrevs.openjdk.org/?repo=valhalla&pr=2064&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8377327
  Stats: 62 lines in 7 files changed: 19 ins; 35 del; 8 mod
  Patch: https://git.openjdk.org/valhalla/pull/2064.diff
  Fetch: git fetch https://git.openjdk.org/valhalla.git pull/2064/head:pull/2064

PR: https://git.openjdk.org/valhalla/pull/2064