Move style docs to qcstyle.DefaultStyle

[enavarro51]

Summary

Move 'style' docs from circuit_drawer and QuantumCircuit.draw to DefaultStyle

Details and comments

Previously the docs for the style dict were duplicated in qiskit.visualization.circuit_drawer and qiskit.circuit.QuantumCircuit.draw. Based on discussions in #5223 and #5269, this PR removes them from those locations and places them in the qiskit.visualization.qcstyle.DefautlStyle class. Links to the DefaultStyle docs are added to the previous locations.

[mtreinish]

This LGTM, but before this will work you'll have to add the DefaultStyle class to the docs. See: https://qiskit.org/documentation/contributing_to_qiskit.html#documentation-structure for more details on how the docs are constructed

[mtreinish]

This likely won't work until we add the default style class to the documentation. Normally you would do this by adding the class to qiskit/visualization/__init__.py's autosummary in the module docstring. If you do that the path will be qiskit.visaulization.DefaultStyle.

[enavarro51]

Thanks. Should be done in a1fd752.

[mtreinish]

Since you added the class to the docs as ~qiskit.visualization.qcstyle.DefaultStyle the path in the docs becomes

Suggested change

	See: :class:`~qiskit.visualization.DefaultStyle` for more
	See: :class:`~qiskit.visualization.qcstyle.DefaultStyle` for more

which I realize is what you had before. I left my previous comment assuming we'd be re-exporting DefaultStyle and add it to the autosummary line as DefaultStyle. But doing this is fine too, so you can switch this back and the link should work fine.

[enavarro51]

Ah, that makes sense. Done in 807b9c9.

[1ucian0]

Thanks!