[lworld] RFR: 8247569: [lworld] Align with spec for <vnew> methods

[Vicente Romero]

Value classes constructor should be named <vnew> instead of <init>. This PR can't be pushed without the corresponding support being available on the VM side

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Commit messages:
 - 8247569: [lworld] Align with spec for <vnew> methods

Changes: https://git.openjdk.org/valhalla/pull/771/files
 Webrev: https://webrevs.openjdk.org/?repo=valhalla&pr=771&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8247569
  Stats: 234 lines in 45 files changed: 88 ins; 6 del; 140 mod
  Patch: https://git.openjdk.org/valhalla/pull/771.diff
  Fetch: git fetch https://git.openjdk.org/valhalla pull/771/head:pull/771

PR: https://git.openjdk.org/valhalla/pull/771