input-surface: Move debug info to separate widget

Move the surface that keeps the debug information (which was phosh-osk-stub's initial purpose) into a separate widget. This makes pos-input-surface focus more in input and also allows us to add new things to the debug surface more easily without getting into conflict with e.g. the completion code.

Let's get this out of the way before merging the completion code.

Signed-off-by: Guido Günther guido.gunther@puri.sm