[InstCombine] fix miscompile from vector select substitution

This is similar to the fix in c590a988 ( PR49832 ), but
we missed handling the pattern for select of bools (no compare
inst).

We can't substitute a vector value because the equality condition
replacement that we are attempting requires that the condition
is true/false for the entire value. Vector select can be partly
true/false.

I added an assert for vector types, so we shouldn't hit this again.
Fixed formatting while auditing the callers.

https://llvm.org/PR50500