[lworld] RFR: 8361302:

[Roger Riggs]

The changes to Class.isValue() resulted in vm crashes. Reverting.

[lworld] Clarify identity vs value in Class, Object, and document limitations of value objects"

This reverts commit 6541b8be1d4c44245cdd62f85a7d7e943b084140.

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Commit messages:
 - Revert "8346307: [lworld] Clarify identity vs value in Class, Objects, and document limitations of value objects"

Changes: https://git.openjdk.org/valhalla/pull/1499/files
  Webrev: https://webrevs.openjdk.org/?repo=valhalla&pr=1499&range=00
  Stats: 265 lines in 12 files changed: 15 ins; 202 del; 48 mod
  Patch: https://git.openjdk.org/valhalla/pull/1499.diff
  Fetch: git fetch https://git.openjdk.org/valhalla.git pull/1499/head:pull/1499

PR: https://git.openjdk.org/valhalla/pull/1499