[SCEV] Add false->any implication

By definition of Implication operator, `false -> true` and `false -> false`. It means that
`false` implies any predicate, no matter true or false. We don't need to go any further
trying to prove the statement we need and just always say that `false` implies it in this case.

In practice it means that we are trying to prove something guarded by `false` condition,
which means that this code is unreachable, and we can safely prove any fact or perform any
transform in this code.

Differential Revision: https://reviews.llvm.org/D98706
Reviewed By: lebedev.ri