udev-builtin-input_id: use heuristics to detect joysticks

udev-builtin-input_id: use heuristics to detect joysticks

Several keyboard devices are erroneously tagged with ID_INPUT_JOYSTICK
because of random buttons they set. For example, the LiteOn Lenovo
Calliope USB Keyboard sets BTN_TRIGGER, BTN_TOP2, BTN_PINKIE and
BTN_BASE, see libinput issue 745 for details.

ID_INPUT_JOYSTICK triggers the uaccess rules, making those keyboards
easily accessible. That's not a problem in the LiteOn example since that
event node doesn't contain the normal keys and eavesdropping on volume
keys is probably not very interesting.

Improve the joystick detection by adding heuristics similar to what
libinput 1.20 uses: check for some specific set of keys that are common
on keyboards but very unlikely on joysticks. If enough of those are
present (or the device has less than 2 axes or joysticks), don't tag it
as joystick.

libinput also checks for > 10 keyboard keys, but this is not done here
to be more conservative.