Fixes#1103
gortsplib/v2 supports multiple formats inside a single track (media). This allows to apply the resizing algorithm to single formats inside medias.
For instance, if a media contains a a proprietary format and an H264 format, and the latter has oversized packets, they can now be resized.
* split data into specialized structs
* move MPEG4-audio decoding into streamTrack
* restore video/audio synchronization in HLS muxer and RTMP server
* log decode errors
* move H264 decoding and re-encoding here from gortsplib
* add tests
* update gortsplib
