[lworld] RFR: 8296491: Implement Object::hashcode for recursively-typed values

[Mandy Chung]

This is a follow-up of JDK-8293321 to complete the implementation for recursively-typed values.

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Commit messages:
 - Implement Object::hashcode for recursively-typed values

Changes: https://git.openjdk.org/valhalla/pull/805/files
 Webrev: https://webrevs.openjdk.org/?repo=valhalla&pr=805&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8296491
  Stats: 280 lines in 2 files changed: 203 ins; 35 del; 42 mod
  Patch: https://git.openjdk.org/valhalla/pull/805.diff
  Fetch: git fetch https://git.openjdk.org/valhalla pull/805/head:pull/805

PR: https://git.openjdk.org/valhalla/pull/805