[lworld] RFR: 8348743: [lworld] GetObjectHashCode crashes with ShouldNotReachHere()

[Alex Menkov]

The change fixes GetObjectHashCode JVMTI function.
Hashcode is the same for all instances of a value class - similar to fix for heap walking functions ([JDK-8310655](https://bugs.openjdk.org/browse/JDK-8310655)). The solution is far from perfect, but it's better than crash

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Commit messages:
 - fix

Changes: https://git.openjdk.org/valhalla/pull/1354/files
  Webrev: https://webrevs.openjdk.org/?repo=valhalla&pr=1354&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8348743
  Stats: 147 lines in 3 files changed: 144 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/valhalla/pull/1354.diff
  Fetch: git fetch https://git.openjdk.org/valhalla.git pull/1354/head:pull/1354

PR: https://git.openjdk.org/valhalla/pull/1354