[X86] Add tests showing failure of combineVectorCompareAndMaskUnaryOp to...

[X86] Add tests showing failure of combineVectorCompareAndMaskUnaryOp to handle 'all-bits' general case

For the sint_to_fp(and(X,C)) -> and(X,sint_to_fp(C)) fold, combineVectorCompareAndMaskUnaryOp only matches X against SETCC (with an all-bits result) when really it could accept anything that ComputeNumSignBits says is all-bits.

Noticed while investigating mask promotion issues in PR45808