[lworld] RFR: 8375319: [lworld] System.identityHashCode wrong for Wrapper classes with -XX:+UseAltSubstitutabilityMethod

[Roger Riggs]

For all value classes, including the wrapper classes,  seed the AltHashCode implementation on the SALT value.

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Commit messages:
 - 8375319: [lworld] System.identityHashCode wrong for Wrapper classes with -XX:+UseAltSubstitutabilityMethod

Changes: https://git.openjdk.org/valhalla/pull/1924/files
  Webrev: https://webrevs.openjdk.org/?repo=valhalla&pr=1924&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8375319
  Stats: 26 lines in 1 file changed: 13 ins; 12 del; 1 mod
  Patch: https://git.openjdk.org/valhalla/pull/1924.diff
  Fetch: git fetch https://git.openjdk.org/valhalla.git pull/1924/head:pull/1924

PR: https://git.openjdk.org/valhalla/pull/1924