docs: clarify buffer ownership/lifecycle
From the API reference (https://docs.pipewire.org/stream_8h.html#ab2ef0e28a1e91816f8015ef9814d18f7), it's not clear who is the owner of the buffer returned by
pw_stream_dequeue_buffer(). In particular,
- If the stream is destroyed while I own a reference to the buffer, does the buffer get deallocated leaving me with a dangling pointer? If not, how do I destroy a buffer if I don't have a reference to a stream?
- Am I allowed to queue a buffer into a different stream than it originated from?
Answering these questions will allow us to write a safe Rust wrapper for the stream and buffer APIs (pipewire-rs#16 (closed))