…lerances

This commit adds a new basis ZSXX to the 1q euler decomposer. This basis
is identical to the ZSX basis except it does an additional
simplification pass so that instead of having 2 sx gates in the
synthesized output a single X gate is used instead.

Fixes Qiskit#5722

…olerances

Make __repr__ use numpy.save/numpy.load to
work around bug in numpy.array2string

This commit merges the zsxx-basis branch from Qiskit#5937 into this branch.
From that PR:

This commit adds a new basis ZSXX to the 1q euler decomposer. This basis
is identical to the ZSX basis except it does an additional
simplification pass so that instead of having 2 sx gates in the
synthesized output a single X gate is used instead.

Fixes Qiskit#5722

Some tests were failing in TestSingleControlledRotationGates due to
different global phase tracking causing an extra P() gate
in some circumstances. Since the CCRZ gates are not minimal in single-qubit
rotations anyway, and should be single-qubit optimized afterwards
I fixed this by changing the test to pass for the slightly longer
result circuit.