Fix issue with ControlFlowOps and cregbundle and mods to circuit drawer testing

[enavarro51]

Summary

Fixes an issue where use of ControlFlowOps would force cregbundle to False.
Changes function calls in "mpl" and "text" drawer tests.

Details and comments

When #10207 and #10414 were done to add display of internal circuits in ControlFlowOps to the mpl and text drawers, the drawings did not properly handle cregbundle=True. This was due to a check for cargs that inadvertently affected ControlFlowOps. In addition, the check was not looking inside the circuits of ControlFlowOps which meant the check could miss composite gates with cargs that should be setting cregbundle=False.

There was a similar cregbundle check due to the use of wire_order that was done at the beginning of the circuit_drawer function. It was appropriate to put the cargs check there as well, but both of these checks create a problem for the mpl and text test suites. test_circuit_text_drawer.py uses _text_circuit_drawer which is a subsidiary function to circuit_drawer. This means the 2 checks described above never get done during the testing, which can cause incorrect output. Similarly for mpl tests which use _matplotlib_circuit_drawer for testing.

This also means we are not really testing the user experience since they use QuantumCircuit.draw or circuit_drawer to display circuits. The solution was to convert the tests suites to use circuit_drawer instead of the subsidiary functions.

It was also discovered that the encoding option for _text_circuit_drawer did not exist in circuit_drawer which meant users could not set it. This was added to circuit_drawer and QuantumCircuit.draw.

In fixing the cregbundle issue in the mpl drawer, it was discovered that the condition lines could, for larger numbers of bits in a creg, overlay the cregbundle info. Minor adjustments were made to the cregbundle display and this is the reason for the extra updated mpl reference images.

A few consistency and cleanup changes left over from #10207 and #10414 were done as well.

[qiskit-bot]

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

• @enavarro51
• @Qiskit/terra-core

[1ucian0]

Based on the amount of changes, I would consider this bugfix for next stable, instead of patch release. But I dont feel super strongly about it.

[jakelishman]

Was this replaced by #10842 and #10869? I can't remember the way the split was going to work.

[enavarro51]

Parts of this were replaced by #10842, but #10869 is a new PR for displaying expressions. The rest of this one will have to be done in new future PRs.

[jakelishman]

Edwin: this appears to have quite a few merge conflicts at the moment - do you know what the status of this PR is now?

[enavarro51]

I'll close it. Half of it is done in #10842 and the rest should be done in new PRs.

[jakelishman]

Ah ok, that definitely makes things easier thanks!