stream: add more timing info

Keep track of queued data in the stream
Pass delay field around to make it possible to know about the raw
software read/write pointer and the hardware one.
Start stream position at 0

src/pipewire/private.h

@@ -227,7 +227,8 @@ struct pw_module {
 struct pw_driver_quantum {
 	uint64_t nsec;			/**< time in nanoseconds */
 	struct spa_fraction rate;	/**< rate */
-	uint32_t position;		/**< current position expressed in rate */
+	uint64_t position;		/**< current position expressed in rate */
+	uint64_t delay;			/**< delay to hardware */
 	uint32_t size;			/**< size of one period expressed in rate */
 };