Structural change to mpl circuit drawer to use class NodeData

[enavarro51]

Summary

Switch to using NodeData class

Details and comments

Following on #10207 and from a suggestion by @jakelishman, this PR switches to using a NodeData class for storing data used in the drawing elements of a circuit and keyed on the node id. So a previous use such as node_data[node]["width"] is now node_data[node].width. This improves the readability of the code, provides for descriptions of the attributes in one place, and allows removal of several initialization checks.

[qiskit-bot]

One or more of the the following people are requested to review this:

• @enavarro51
• @Qiskit/terra-core

[coveralls]

Pull Request Test Coverage Report for Build 5638946759

• 42 of 88 (47.73%) changed or added relevant lines in 1 file are covered.
• 24 unchanged lines in 3 files lost coverage.
• Overall coverage decreased (-0.02%) to 85.907%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
qiskit/visualization/circuit/matplotlib.py	42	88	47.73%

Files with Coverage Reduction	New Missed Lines	%
crates/qasm2/src/lex.rs	3	91.14%
qiskit/visualization/circuit/matplotlib.py	3	50.73%
crates/qasm2/src/parse.rs	18	96.18%

Totals
Change from base Build 5631006520:	-0.02%
Covered Lines:	73016
Relevant Lines:	84994

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💛 - Coveralls

[jakelishman]

Thanks Edwin, this makes that whole node_data object a bit less magical - much easier to see what's actually known about each node, and to have a common place to see documentation / comments on the different parts.