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>