[InstCombine] allow more folds more multi-use selects

The 'and' case showed up in a recent bug report and prevented
more follow-on transforms from happening.

We could handle more patterns (for example, the select arms
simplified, but not to constant values), but this seems
like a safe, conservative enhancement. The backend can
convert select-of-constants to math/logic in many cases
if it is profitable.

There is a lot of overlapping logic for these kinds of patterns
(see SimplifySelectsFeedingBinaryOp() and FoldOpIntoSelect()),
so there may be some opportunity to improve efficiency.

There are also optimization gaps/inconsistency because we do
not call this code for all bin-opcodes (see TODO for ashr test).