RTMP Go Away: Lossless reconnections for live streaming

Introduced the RTMP Go Away mechanism, a new feature for the Real Time Messaging Protocol (RTMP) that allows live servers to signal an impending connection termination to clients. This enables clients to reconnect at a logical media boundary (e.g., next keyframe) with zero data loss, reducing reconnection times from up to 20 seconds to minimal interruption. The contribution includes spec updates to the RTMP connect packet and a new protocol message type for the go away signal, along with a reference implementation in FFmpeg.