[lworld] RFR: 8328438: [lworld] Reimplement VTAssignability for JEP401

[Frederic Parain]

Update test.

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Commit messages:
 - Update assignability test

Changes: https://git.openjdk.org/valhalla/pull/1168/files
  Webrev: https://webrevs.openjdk.org/?repo=valhalla&pr=1168&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8328438
  Stats: 13 lines in 1 file changed: 9 ins; 1 del; 3 mod
  Patch: https://git.openjdk.org/valhalla/pull/1168.diff
  Fetch: git fetch https://git.openjdk.org/valhalla.git pull/1168/head:pull/1168

PR: https://git.openjdk.org/valhalla/pull/1168