In-place editing toolbars in DOM not removed after stopping in-place editing

Reported at #1962190: In-place editing toolbars in DOM not removed after stopping in-place editing (was: Tidy up HTML after toggling Quick Edit) for D7 version of Edit module, since D7/D8 Edit's JS is >95% identical, the same bug exists in D8.

If you start quick editing, stop it, start it, stop it, etc. for a certain entity, then you will notice that Edit doesn't properly clean up after itself:

This was introduced in the last big refactoring; the toolbars are now persisted for the entire duration of the in-place editing process. Previously, they were continuously created and removed upon hover/editing, which results in many more DOM operations, and is thus slower.