[DAG] Refactor X86 combineVSelectWithAllOnesOrZeros fold into a generic DAG Combine

[RKSimon]

combineVSelectWithAllOnesOrZeros folds vselect(cond, 0/-1, X) and vselect(cond, X, 0/-1) style patterns into logic operations when the cond is the same width and ZeroOrNegativeOneBooleanContent

We should be able to perform this generically in DAGCombiner (with suitable freezing which seems to be missing from the x86 version)

[RKSimon]

CC @woruyu - not sure if you'd want to take this on but its not dissimilar to the foldMaskedMerge patches you've tried in the past.

[woruyu]

@RKSimon , of course，I'm glad to, thank you!