pulse: Handle timed out streams

If we don't get a link on a stream, we might never send a create stream
reply. The client handles this fine by timing out after 30s and dropping
the stream, but the server holds on to the pw_stream forever (or until
the client quits).

Let's add a timer to clean up such streams on the server.

Fixes: https://gitlab.freedesktop.org/pipewire/pipewire/-/issues/4901

src/modules/module-protocol-pulse/stream.h

@@ -50,6 +50,7 @@ struct stream {
 
 	struct pw_stream *stream;
 	struct spa_hook stream_listener;
+	struct spa_source *timer;
 
 	struct spa_io_position *position;
 	struct spa_ringbuffer ring;