[lworld] RFR: 8364447: [lworld] Save isIdentity in a field of Class

[Coleen Phillimore]

This change saves an 'identity' field in the j.l.Class for easy checks and inlining.
Tested with tier1-4.

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Commit messages:
 - 8364447: [lworld] Save isIdentity in a field of Class

Changes: https://git.openjdk.org/valhalla/pull/1738/files
  Webrev: https://webrevs.openjdk.org/?repo=valhalla&pr=1738&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8364447
  Stats: 23 lines in 5 files changed: 11 ins; 6 del; 6 mod
  Patch: https://git.openjdk.org/valhalla/pull/1738.diff
  Fetch: git fetch https://git.openjdk.org/valhalla.git pull/1738/head:pull/1738

PR: https://git.openjdk.org/valhalla/pull/1738