[Comb] ICmp folds missing for CEQ/CNE/WEQ/WNE

[fabianschuiki]

The comb dialect is missing folds for the new SV case equality and wildcard equality checks (ceq, cne, weq, wne) in CombFolds.cpp, specifically applyCmpPredicate, applyCmpPredicateToEqualOperands, and ICmpOp::canonicalize.

These might just work like the eq and ne cases since the SV flavors mostly differ for X and Z, which aren't modeled in anything that the folds would see (I think at least). This might need some additional thoughts and documenting the exact semantics of these comparisons.