[lworld] RFR: 8376708: [lworld] Missed Ideal optimization around CmpL

[Benoît Maillard]

This PR adresses a missed optimization in `CmpLNode::Ideal`. It occurs when when we encode a pointer comparison as `CmpL(OrL(left, right), 0L)` (which essentially translates to "both operands are null") during parsing in `do_acmp`, and this comparison can later be folded to a constant in `CmpLNode::Ideal` because one of the operands has a `NotNull` type. This optimization hides behind `can_reshape`, so it can only be carried out during IGVN and not during the initial GVN pass.  To fix this, we just need to make sure to add the compare to the worklist during parsing.

### Testing
- [x] GitHub Actions
- [x] tier1-3, plus some internal testing

Thank you for reviewing!

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Commit messages:
 - Comment
 - Remove debug comment
 - Add summary
 - Add to worklist in parsing
 - Add test

Changes: https://git.openjdk.org/valhalla/pull/2145/files
  Webrev: https://webrevs.openjdk.org/?repo=valhalla&pr=2145&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8376708
  Stats: 66 lines in 2 files changed: 66 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/valhalla/pull/2145.diff
  Fetch: git fetch https://git.openjdk.org/valhalla.git pull/2145/head:pull/2145

PR: https://git.openjdk.org/valhalla/pull/2145