feat: Add basic USB-Camera support

[mryel00]

(Updated version)
This adds one new start parameter:

• --camera_num -n to start spyglass with a specific camera. You can see all available cameras with the python command Picamera2.global_camera_info(). A start parameter to show this message should be added in the future.

This also adds the ability to use USB cameras instead of only CSI (Pi cameras). The whole filestructure of cams got updated to make use of inheritance for that reason.

Note:
USB cams run terribly atm with libcamera and not all controls are available to use. Therefore they shouldn't be used with Spyglass.

[roamingthings]

I've created #23 as feature request for this

[roamingthings]

My thoughts regarding the implementation:

• Afaik the filename convention for python is lowercase_with_underscore.py. This would mean usbCamera.py becomes usb_camera.py and usbServer.py becomes usb_server.py.
• Looking at (usb_)camera.py the main difference seems to be the controls and main configuration. Maybe it would be better to introduce a class for the camera and have a method the get these values for each camera
• run_server should become part of the camera class for the same reason.
• It would be better to have an abstract camera class and a PiCamera and UsbCamera subclass.

@mryel00 Let me know if you would like to have some help regarding the implementation

[mryel00]

Somehow I again forgot about the naming conventions 😅
You are right about the implementation way. That should be changed. This was more like a proof of concept and only a quick dirty way to implement and test it.
I would appreciate your help implementing it.

[roamingthings]

Looks good