[InstCombine] fold power-of-2 ctlz/cttz with inverted result

When X is a power-of-two or zero and zero input is poison:
ctlz(i32 X) ^ 31 --> cttz(X)
cttz(i32 X) ^ 31 --> ctlz(X)

https://alive2.llvm.org/ce/z/Cs7sFE