Add SRT/RIST and update to FFMpeg 6

[guilletrejo]

• Add SRT version 1.5.3 (latest to date)
• Add RIST version 0.2.10 (latest to date)
• Update FFMpeg to 6.0

I tested and compiled with this additions and the 3 binaries (ffmpeg, ffplay, ffprobe) still were static, but just in case, test it to be sure.

[zimbatm]

Thanks!