[Instsimplfy] X == Y ? 0 : X - Y --> X - Y

Alive2: https://alive2.llvm.org/ce/z/rPN1GB
Fixes: https://github.com/llvm/llvm-project/issues/62238



Depends on D150377

Signed-off-by: Jun Zhang <jun@junz.org>

Differential Revision: https://reviews.llvm.org/D150378