Change operator comparison from np.array_equal to np.allclose (#6473)

[mattwright99]

Summary

Fixes #6473

Details and comments

Optimize1qGatesDecompositions would not optimize single qubit gates if they are sufficiently close to the identity (see #6473 for example). This was fixed by replacing the np.array_equals function with the np.allclose function to compare the operator to the identity. We use an absolute threshold of 1e-15.

New output:

>>> import qiskit as qk
>>> from qiskit.transpiler.passes import Optimize1qGates, Optimize1qGatesDecomposition
>>> qc = qk.QuantumCircuit(1)
>>> qc.u1(1e-17, 0)
>>> qc.draw()
     ┌───────┐
q_0: ┤ U1(0) ├
     └───────┘
>>> Optimize1qGatesDecomposition(basis=['u1', 'u2', 'u3'])(qc).draw()

q_0:

>>>      

[levbishop]

Looks good can you add a release note?

[mattwright99]

@levbishop should be good now!

[levbishop]

Thanks for this