Force stop a channel (will force stop all connected engines and rtsp-pull ingests)

Stops all connected engines and all connected rtsp-pull ingests of the channel immediately, skipping the graceful shutdown: the engines are torn down right away without closing their playlists first, so viewers may see playback fail instead of the stream ending cleanly. Works from any non-stopped state, including while engines are stopping after a regular stop. Engines report stopping until the teardown has completed (usually a few seconds), then stopped. Prefer POST /channels/{id}/stop unless the engines have to be gone immediately.