Alarm on smart detections
### Describe the feature request

Unifi has decent smart detections (e.g., person detected). I would love if I could use these smart detections as a trigger for a homekit home alarm.

I think most of the DIY/off-the-shelf alarm solutions are too onerous. They have door sensors, window sensors, and much more which depending on your home design, might be a lot of devices to maintain and deal with. In my townhome for example, there's multiple windows and doors on the first floor, but instead of like 4 door sensors and 8 window sensors, I prefer having a single camera looking down the stairwell that triggers the alarm if a human is detected.

### Describe the proposed solution

1. Add an alarm switch to the protect system. I'm not sure if this would have to be associated with a device or it'd just be virtual with the bridge or something. But you need to be able to set the alarm to active or inactive.
2. Allow the user to select which cameras and/or type of smart detections (person, vehicle, etc) are relevant to trigger the alarm, if the alarm is active.
3. Actually trigger the alarm based on #2 configuration and smart detections as they come in.

I would expect to configure what happens if the alarm is triggered in homekit using automations/scenes.

### Describe alternatives you have considered to the enhancement

My current alternative is using Aqara G3 cameras for this. Basically I have one of these at each major entryway to my home and if they detect a person while the alarm is active, it sets of the alarm. This integrates well with homekit and works fine, but I'd much rather standardize on protect vs Aqara.