Inputmethod.cpp: Introduce 3 state mode for virtual keyboard

Yelsin Sepulvedarequested to merge
yorisoft/kwin:work/yorisoft/3_states_virtual_keyboard into master

Currently forceActivate() doesn't work as expected.
Due to event filtering it only works for input()->touch() & input()->tablet() events.

As suggested in !3895, this MR is to fix/create 3 states for the virtual keyboard:

State
Off
TouchOnly
On
Edited by Yelsin Sepulveda

Merge request reports