tablet: centralize the libwacom handling

tablet: centralize the libwacom handling

Instead of re-creating the the libwacom device from the database every
time we need it let's create it once during tablet|pad_init and pass it
down to the functions.

This allows us to have one point per tablet/pad where we can log an
error if the device is not supported by libwacom - previously this was
printed during the left-handed setup.

Part-of: <https://gitlab.freedesktop.org/libinput/libinput/-/merge_requests/1073>