input: always use mouse emulation for tablet tool mouse

input: always use mouse emulation for tablet tool mouse

Using mouse emulation for a tablet tool mouse is just a practical
decision to let such a tool work more smootly, e.g. it avoids weird
menu issues in GTK applications. Since such a tool doesn't have
pen specifix axis like pressure or distance, no functionality is lost.

A solution fully in line with the protocol, which would pass the tool
mouse buttons to the client, would leave us with  e.g. non-working
buttons in current GTK4 since they don't handle the buttons
reported from the tool mouse.
May be this changes in future. But for now, let's just be practical.