[InstCombine] add fold (X > C - 1) ^ (X < C + 1) --> X != C

Considering the correctness of this pattern, we should avoid that C - 1
is non-negative and C + 1 is negative.

Alive2: https://alive2.llvm.org/ce/z/c_rBaq

Reviewed By: spatel

Differential Revision: https://reviews.llvm.org/D129622