hwdb: add MOUSE_WHEEL_CLICK_COUNT for non-integer click angles (#4440)

hwdb: add MOUSE_WHEEL_CLICK_COUNT for non-integer click angles (#4440)

MOUSE_WHEEL_CLICK_ANGLE has been an integer, and at least libinput (probably
the only user) parses it as strict integer. For backwards compatibility, we
cannot change it to a decimal number now.

Add a new property to list the number of clicks for a full 360 degree
rotation, to be specified in addition to the old click angle property. Clients
can prefer the new one where available and calculate the decimal value to
whatever precision they want.