[lworld] RFR: 8294312: [lworld] Add java.util.Objects.isIdentityObject [v2]

[Roger Riggs]

> Add `java.util.Objects.isIdentityObject(obj)` and update tests.
> 
> Correct j.l.Class.isIdentity() and .isValue() to correctly identify all arrays as identity objects.
> (The modifiers for array classes do have not reliable ACC_IDENTITY or ACC_VALUE bits).
> 
> Updated ValhallaFeaturesTest to use junit.

Roger Riggs has updated the pull request incrementally with one additional commit since the last revision:

  Review comment updates related to ValhallaFeatures.isEnabled().
  And javadoc cleanup

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Changes:
  - all: https://git.openjdk.org/valhalla/pull/770/files
  - new: https://git.openjdk.org/valhalla/pull/770/files/3612a507..ff48dae1

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=valhalla&pr=770&range=01
 - incr: https://webrevs.openjdk.org/?repo=valhalla&pr=770&range=00-01

  Stats: 18 lines in 4 files changed: 7 ins; 0 del; 11 mod
  Patch: https://git.openjdk.org/valhalla/pull/770.diff
  Fetch: git fetch https://git.openjdk.org/valhalla pull/770/head:pull/770

PR: https://git.openjdk.org/valhalla/pull/770