[X86] Fold AND(SRL(X,Y),1) -> SETCC(BT(X,Y))

As noticed on PR39174, if we're extracting a single non-constant bit index, then try to use BT+SETCC instead to avoid messing around moving the shift amount to the ECX register, using slow x86 shift ops etc.

Differential Revision: https://reviews.llvm.org/D122891