Fixes for using FFmpeg 6.1 due to deprecations. Uses `#if` macros to
allow builds for using older versions of FFmpeg.
This commit replaces usage of `av_stream_add_side_data(...)` with
`av_packet_side_data_add(...)`, as the former was deprecated in favor of
the latter.
The FFmpeg commit that deprecated `av_stream_add_side_data(...)` is [1].
The FFmpeg commit that introduced `av_packet_side_data_add(...)` is [2].
Note that the deprecation commit is after the new API function. The
commit in between [3] appears to be changes that migrates to the usage
of the new API function.
[1]: avformat/avformat: use the side data from AVStream.codecpar
5432d2aaca
[2]: avcodec/packet: add generic side data helpers
74279227dd
[3]: avcodec/codec_par: add side data to AVCodecParameters
21d7cc6fa9