RTMP Go Away: Lossless reconnections for live streaming

What this post added

Introduced RTMP Go Away, a mechanism to signal live server connection termination to clients at logical media boundaries, enabling lossless reconnections. This involves spec updates to the RTMP connect packet and a new protocol message type for the go away signal. A reference implementation in FFmpeg allows clients to reconnect at the next keyframe. The rollout is safe, as the go away message is only sent to clients that have indicated support for the new feature.