[lworld] RFR: 8272041: [lworld] CDS heap dump fails with primitive objects

[Ioi Lam]

Two simple fixes to handle primitive objects when dumping the CDS heap:

- When dumping the objects, we enter them into a hashtable. Do not use `oopDesc::identity_hash()` as the hashcode for this table.
- When resetting the header of archived objects, do not call `oopDesc::identity_hash()` on primitive objects.

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Commit messages:
 - 8272041: [lworld] -Xshare:dump fails when classlist contains primitive classes

Changes: https://git.openjdk.java.net/valhalla/pull/525/files
 Webrev: https://webrevs.openjdk.java.net/?repo=valhalla&pr=525&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8272041
  Stats: 12 lines in 1 file changed: 3 ins; 0 del; 9 mod
  Patch: https://git.openjdk.java.net/valhalla/pull/525.diff
  Fetch: git fetch https://git.openjdk.java.net/valhalla pull/525/head:pull/525

PR: https://git.openjdk.java.net/valhalla/pull/525