[lworld] RFR: 8282106: [lworld] IdentityException should identify the value class

[Frederic Parain]

Improve the message of IdentityException by including the class of the instance that triggered the exception.

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Commit messages:
 - Improve IdentityException message

Changes: https://git.openjdk.org/valhalla/pull/1150/files
  Webrev: https://webrevs.openjdk.org/?repo=valhalla&pr=1150&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8282106
  Stats: 118 lines in 10 files changed: 109 ins; 0 del; 9 mod
  Patch: https://git.openjdk.org/valhalla/pull/1150.diff
  Fetch: git fetch https://git.openjdk.org/valhalla.git pull/1150/head:pull/1150

PR: https://git.openjdk.org/valhalla/pull/1150