Refactor lima decoding

This updates decoding lima colour frames to use code (fairly) consistent with bliss. It provides the ability to opencv decode a few different frame types, scale images based on bpp (i.e. 12bpp bayer images -> 16bit), and rotate images based on lima.image_rotation. Also adds a series of tests so check decoding is actually working in conjunction with the https://gitlab.esrf.fr/ui/video-streamer-mpeg tests This makes it a lot easier in future to add new pixel formats.