Remove dependency on OpenCV

[mrozycki]

OpenCV is a large C++ library that has been causing us various issues over time, including problems building on Windows, constant rebuilds despite no changes etc.

Given that we only use a tiny fraction of what OpenCV has to offer, we might be able to replace that with either native Rust libraries or manually rewrite a couple of OpenCV functions into pure Rust, to avoid those issues in the future.

It seems that using imageproc for image processing and nokhwa for camera control might be enough for our use case.

[mrozycki]

nokhwa seems to have trouble working on macOS: l1npengtul/nokhwa#100

This has to be postponed until those issues are resolved, or we find another capture library.

[mrozycki]

nokhwa is unfortunately still not ready, and at this point it doesn't seem like it's going to be anytime soon. We have found a simpler crate, but with enough functionality to support our use case: payload/kamera.