We need to defer config application to the first manage_start event
using a should_manage flag so that all *_support events have arrived
before we try applying the configs
This commit also has two other fixes
- fixes a potential use-after-free by telling InputDevice when a
LibinputDevice is .removed.
- fix logFn (removed "if (scope != .default) return;")
I used kwm to help figure out the manage pattern for the input config.
Link to kwm: https://github.com/kewuaa/kwm
Right now, the support is still incomplete (no way to set config) but
we get the devices and set them up and handle current/support events
for the river_libinput_device_v1 devices.