Move output chunking from gst_rtmp_connection_queue_message into
gst_rtmp_connection_start_write, which effectively moves it from the
streaming thread into the loop thread.
This allows us to handle the outgoing chunk-size message (which is
generated by changing the future chunk-size property) properly, which
could come from any other thread.
Serializes an RTMP message into a series of chunks, all in one buffer.
Similar to what gst_rtmp_connection_queue_message does to serialize
into a GByteArray.
The message buffers are created using `gst_rtmp_message_new` and thus
always contain a GstRtmpMeta. Add checks to appease Coverity's static
analysis.
CID 1455596
CID 1455384
