[ValueTracking] Improve analysis of knownbits from incoming phi edges.

Just fill in missing cases (TODO) for `ugt`, `uge`, `sgt`, `sge`,
`slt`, and `sle`. These are all in the same spirit as `ult`/`uge`, but
each of the other conditions have different constraints.

Proofs: https://alive2.llvm.org/ce/z/gnj4o-

Differential Revision: https://reviews.llvm.org/D157800