[lworld] RFR: 8280164: [lworld] Generate Preload attribute to enumerate value classes encountered

[Srikanth Adayapalam]

Modelled after InnerClasses attribute generation, we may be generating more information than necessary/useful but this is initial cut

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Commit messages:
 - Fix trailing white space
 - 8280164: [lworld] Generate Preload attribute to enumerate value classes encountered

Changes: https://git.openjdk.java.net/valhalla/pull/605/files
 Webrev: https://webrevs.openjdk.java.net/?repo=valhalla&pr=605&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8280164
  Stats: 266 lines in 11 files changed: 260 ins; 0 del; 6 mod
  Patch: https://git.openjdk.java.net/valhalla/pull/605.diff
  Fetch: git fetch https://git.openjdk.java.net/valhalla pull/605/head:pull/605

PR: https://git.openjdk.java.net/valhalla/pull/605