Afform - ensure dragging classes are removed when not sorting

[colemanw]

Overview

Fixes an annoying UI glitch in Afform where the screen can appear "locked" or "frozen" after dragging fields into a fieldset.

Comments

This is hard to reproduce on purpose but very annoying when it happens to you. It's such a simple fix I think we should merge it into the RC. I'm usually able to reproduce it by dragging a field from the palette on the left into a container within a fieldset.

Technical Details

Most of this PR is just adding code comments. Only functional change it to listen to more events.

[civibot]

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[rbaugh]

Came across this odd behavior as well but thought it was something on my end and just refreshed the page. After knowing it was a re-producible bug, I was able to replicate this as well. After applying this PR, I don't seem to get the issue. Can add field to container and click around and it retains ability to edit field

[eileenmcnaughton]

Thanks @rbaugh - appreciate you taking the time to test this PR - I'm merging based on your testing