mem: Add tag to memmap

Add a tag field when creating a memmap so that we can do lookup on it.
This makes it easier to implement the tracking of mappings for io areas.
Remove custom io memory tracking and use the tags.

Add flags to spa_chunk to make data corrupted. The flags on the buffer
stay constant for the life of the buffer. Add flags to mark memory
readable and writable. Mark memory readonly in v4l2-source.

Pass the daemon activation area to the client in the transport event.
This never changes and need to be handled differently from the other
activation areas.

Use the right flags when importing memory.

Add the (desired) memory type to mempool_alloc.

improve some debug.

src/extensions/client-node.h

@@ -71,11 +71,17 @@ struct pw_client_node_proxy_events {
 	 * \param node_id the node id created for this client node
 	 * \param readfd fd for signal data can be read
 	 * \param writefd fd for signal data can be written
+	 * \param mem_id id for activation memory
+	 * \param offset offset of activation memory
+	 * \param size size of activation memory
 	 */
 	int (*transport) (void *object,
 			  uint32_t node_id,
 			  int readfd,
-			  int writefd);
+			  int writefd,
+			  uint32_t mem_id,
+			  uint32_t offset,
+			  uint32_t size);
 	/**
 	 * Notify of a property change
 	 *