[lworld] RFR: 8373930: [lworld] Restore Objects.equals use of identity check [v2]

[Roger Riggs]

> Revert "8366841: [lworld] Objects.equals without identity comparison".  (Almost all)
> Removing the condition on --enable-preview.
> Correct the .equals method in test SimplValueGraphs.SimpleValue.

Roger Riggs has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains three additional commits since the last revision:

 - Reverted to remove the no longer unnecessary @ForceInline.
   Update copyright.
 - Merge branch 'lworld' into 8373930-objects-equals-revert
 - Restore the mainline implementation of Objects.equal
   removing the condition on --enable-preview.
   Correct the .equals method of SimplValueGraphs.SimpleValue.
   Revert "8366841: [lworld] Objects.equals without identity comparison"

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Changes:
  - all: https://git.openjdk.org/valhalla/pull/1836/files
  - new: https://git.openjdk.org/valhalla/pull/1836/files/9aa1f037..2cea111f

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=valhalla&pr=1836&range=01
 - incr: https://webrevs.openjdk.org/?repo=valhalla&pr=1836&range=00-01

  Stats: 30884 lines in 467 files changed: 20759 ins; 8200 del; 1925 mod
  Patch: https://git.openjdk.org/valhalla/pull/1836.diff
  Fetch: git fetch https://git.openjdk.org/valhalla.git pull/1836/head:pull/1836

PR: https://git.openjdk.org/valhalla/pull/1836