searchbar: Don't activate type-to-search when focusing entries
Currently using GtkSearchBar:key-capture-widget steals focus from unrelated entries within the key capture widget, which is a common case when the key capture widget is the window containing the search bar.
In theory it can be fixed by switching the propagation phase to bubble, but there's a good chance that keypresses will then be intercepted by some other widget when not wanted.
So, instead do a hack and check the type of the focused widget, skipping
if it's a GtkEditable or GtkTextView, and additionally has the editable
property set to TRUE.
Fixes #3606 (closed)
CC @carlosg