buffer: don't use ringbuffer in chunk

We can't use a ringbuffer on the chunk because it implies the
consumer would write to it to update the read position, which we
can't do because the chunk is read-only and might even be shared.
Go back to offset/size pairs, which can sortof do the same thing
if we want later when we keep a non-shared read pointer in the
consumer.
Keep alsa timestamp around and filled state for future.
mmap the input port meta/data/chunk as read-only.
Only do clock update requests when asked.

src/modules/module-client-node/transport.c

@@ -21,6 +21,7 @@
 #include <errno.h>
 #include <sys/mman.h>
 
+#include <spa/utils/ringbuffer.h>
 #include <pipewire/log.h>
 #include <extensions/client-node.h>
 

src/modules/module-jack/jack-node.c

@@ -305,7 +305,9 @@ static int driver_process_output(struct spa_node *node)
 		in_io->status = SPA_STATUS_NEED_BUFFER;
 	}
 
-	spa_ringbuffer_set_avail(&out->outbuf->datas[0].chunk->area, ctrl->buffer_size * sizeof(int16_t) * 2);
+	out->outbuf->datas[0].chunk->offset = 0;
+	out->outbuf->datas[0].chunk->size = ctrl->buffer_size * sizeof(int16_t) * 2;
+	out->outbuf->datas[0].chunk->stride = 0;
 
 	spa_hook_list_call(&nd->listener_list, struct pw_jack_node_events, push);
 	gn->ready[SPA_DIRECTION_INPUT] = gn->required[SPA_DIRECTION_OUTPUT] = 0;