Avoid skipping channels in pulse visualizer

[wshanks]

Summary

This PR fixes some cases where the pulse visualizer would skip some channels.

Details and comments

inds is a set that is iterated over and compared to sorted lists that get their values popped off the end when they match. I guess typically inds has iterated in a way that matches the sorting of the lists so this wasn't noticed before, but the order is random in principle. This PR is a quick fix to sort inds so it matches the ordering of the lists. This problem was first noticed in Qiskit Slack.

This is a pretty small change -- we could add a release note or tests (I haven't looked at the tests for this part of the code) if they seemed worthwhile.

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[jakelishman]

If it's a bug fix, we always do a release note - since it got noticed in the Slack, it definitely warrants one! It doesn't really matter how easy / small the internal code change was.

[coveralls]

Pull Request Test Coverage Report for Build 3309767833

• 2 of 2 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 84.412%

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Totals
Change from base Build 3300600629:	0.0%
Covered Lines:	61703
Relevant Lines:	73097

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💛 - Coveralls

[nkanazawa1989]

LGTM. I'll approve after release note.

[wshanks]

Okay, I found the relevant test and modified it to fail. All the tests in the class use the same set of channels and I didn't want to have to update every test so I just modified the channel list in the one test to get it to fail. If that's too weird, maybe we can just drop that commit. It was a nice sanity check that the fix actually changed a fail into a pass.

I also added a release note. I opened #8981 because it seemed cleanest to reference an issue in the release note.

[nkanazawa1989]

close #8981

[nkanazawa1989]

LGTM thanks for adding test and note.

[wshanks]

@nkanazawa1989 Should we have labeled this with "stable backport potential"?