imcontextwayland: Set up OSK activation gesture on non text widgets

imcontextwayland: Set up OSK activation gesture on non text widgets

With GtkText and GtkTextView (and in extension, all their subclasses)
handling OSK activation activation, this gesture is only useful for
all text input widgets that are not subclasses of these 2 widgets,
e.g. the VTEs and crosswords of the world.

These still do need a hand in handling OSK activation, so only
set up the gesture for such cases.