Improve OpenCV camera backend

[Starbuck5]

I believe there a few problems with it now.

Problems:

• OpenCV needs an explicit backend passed in now?
• OpenCV can report webcam FPS as 0, leads to a divide by zero in the opencv backend

I'd like someone to investigate these and verify functionality. You can select the opencv backend by passing "opencv" into pygame.camera.init's backend argument.

[PurityLake]

I will look in to this today

[PurityLake]

After some testing with the opencv-python.

Not much has changed really as regards initialisation so I don't think a backend needs to be passed in. We solely rely on cv2.VideoCapture and from what I am seeing it is possible to create a cv2.VideoCapture with and optional API preference. So when we use cv2.VideoCapture(0), it is equivalent to using cv2.VideoCapture(0, cv2.CAP_ANY).

In most cases the default settings work for most people but I have read in certain places that the API can matter for certain machines. The last piece of information there I have not been able to confirm on my end, pretty much adding any supported and available API caused no difference in the capture rate of my webcam. Although I suppose it would be silly to assume for that for all webcams.

The framerate issues seems to be mostly due to incorrect configurations of opencv although it may be worth adding a check for that with a specific warning or error thrown letting the user know the issue rather than leaving a not so informative DivideByZeroError.