[lworld] RFR: 8279672: [lworld] Implement semantic checks for value classes

[Srikanth Adayapalam]

Push down various sematic/behavioral restrictions/checks and the associated diagnostics from primitive to value classes.

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Commit messages:
 - Test changes for JDK-8279672
 - 8279672:  Implement semantic checks for value classes

Changes: https://git.openjdk.java.net/valhalla/pull/597/files
 Webrev: https://webrevs.openjdk.java.net/?repo=valhalla&pr=597&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8279672
  Stats: 205 lines in 26 files changed: 132 ins; 12 del; 61 mod
  Patch: https://git.openjdk.java.net/valhalla/pull/597.diff
  Fetch: git fetch https://git.openjdk.java.net/valhalla pull/597/head:pull/597

PR: https://git.openjdk.java.net/valhalla/pull/597