containments/desktop: fix single-click to rename

FolderView has a feature that allows the user to single-click the label of an already selected item to trigger renaming that item (given a particular combination of settings), mirroring similar functionality in Dolphin. This is, again as in Dolphin, supposed to not apply to cases where the label is double-clicked, which should open the double-clicked file. However, the detection of double-clicks does not work: it relies on the doubleClickInProgress property, which is set later in the event handler (and never reached in this case as the handler returns early), and so is almost always false (unless the clicked element changes mid- double-click).

This change modifies the event handling logic to instead use the regular logic to wait for a double-click, and triggers the renaming function from the timer if applicable.

I think this is a bugfix (wrt the clear original intention of the code), so should be 6.2 material.

BUG: 493124 FIXED-IN: 6.2