Cell and editing: problems when scrolling

to reproduce, use the example code in RT-15205
- start editing an arbitrary cell
- scroll the cell out of visible area by clicking on scrollbar

Issue 1:
- scroll cell back into visible area by clicking on scrollbar
expected: cell still editing
is: cell editing terminated

Issue 2:
(scroll back or not, doesn't make a difference)
- double click to start an edit
expected: clicked cell is editing
is: selected only, no editing

1 is a usability issue: users should be allowed to look-around while editing, scrolling is a means to do so. Actually, they expect an edit to stay alive much more often than we as developers do :-)
2 looks like the cell is in some indeterminate editing state when it was terminated in scrolling, which prevents it from starting again

Addendum:
actually, 2 looks like the virtualization is thoroughly confused -
- edit first row
- scroll away several items until the data of the first row is shown in the last row (don't worry - it's not a data corruption, just a visual artefact :-)