node: Add port_info event

Add a port_info event. With this, we get updates to ports pushed to
us, which is more convenient and also allows for better dynamic
add/remove of ports.
We don't need to the PortChanged event anymore
We can remove the get_port_ids/get_n_ports/port_get_info methods.
Update plugins

src/modules/module-link-factory.c

@@ -113,7 +113,7 @@ static struct pw_port *get_port(struct pw_node *node, enum spa_direction directi
 		if (port_id == SPA_ID_INVALID)
 			return NULL;
 
-		p = pw_port_new(direction, port_id, NULL, 0);
+		p = pw_port_new(direction, port_id, 0, NULL, 0);
 		if (p == NULL)
 			return NULL;