FS-7519 FS-7517: looks like decoders don't decode FU-A bit steams, this is a simple implementation that works with some FU-A bit streams, mod_av works better most cases

FS-7500: factor out the write_image callback and fix the vlc video endpoint to setup and match the audio params of the A leg when bridged

FS-7500: reduce CNG frames on video and move debug from mod_fsv to the core with a flag to enable it since the raw packet is not available anymore when you set DECODED READ flag

FS-7500: reverse default for CF_VIDEO_ECHO to false and now it must be enabled when desired instead of disabled when not needed