[SelectOpt] Don't treat LogicalAnd/LogicalOr as selects

A `select i1 %c, i1 true, i1 %d` is just an or and a `select i1 %c, i1 %d, i1 false`
is just an and. There are better treated as such in the logic of SelectOpt, allowing
the backend to optimize them to and/or directly.

Differential Revision: https://reviews.llvm.org/D138490