Update qcircuit_diagram_info.py Draft

[Shadimrad]

This is an attempt to resolve "Support common notations in circuit_to_latex_using_qcircuit #4685".
I am going to change:

• the tests
• the multi-controlled X gate.

However, I thought to ask for a review of the changes that I have made, to know whether they make sense and follow the contribution guidelines or not before I go on with the rest. Any advice is so much appreciated.

[google-cla]

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