The optimize 1q gates pass currently only operates on u1, u2, u3 (or a
subset of that), however the u gate is interchangeable with the u3 gate
and the pass can be run if there is a u in the basis just as easily as
if it were a u3. This comes up for backends with overcomplete basis
sets, like Aer, which can have u and u3 in the same circuit. The
optimization pass will not simplify those gates despite it being
possible.

Just as U and U3 are interchangeable, U1 and P are also interchangeable.
This commit makes the same change to the Optimize1QGates pass done
earlier for supporting U for U1 and P so that if will work for a basis
where P is used instead of U1.