Update API usage, incorporate new features, and refactor a bit:
- Use new progress callback to show progress bar
- Use new frame info functions to get timecodes/keyframes instead of
manually decoding
- Use new tracklist API to show track selection dialogs
- Expose option of whether to apply RFF
- Show a warning when bestsource had to revert to linear decoding
- Reuse the swscale context across frames and ensure the format
stays constant
- Add xxhash wrap
- No longer mark the bestsource video provider as slow
