This changes the behavior of bindings to make the `BINDING_LOCKED` flag
conflicting, which will allow for both unlocked and locked bindings.
If there are two matching bindings and one has `--locked` and the other
does not, the one with `--locked` will be preferred when locked and
the one without will be preferred when unlocked.
If there are two matching bindings and one has both a matching
`--input-device=<input>` and `--locked` and the other has neither, the
former will be preferred for both unlocked and locked.
This also refactors `get_active_binding` in `sway/input/keyboard.c`
to make it easier to read.
6afb392823