Make an eventfd for each node and listen for events when the node
is activated.
Reorganize some graphs links to make it possible to activiate nodes
by signaling the eventfd
Pass the peer node to each remote node and let the remote node
directly activate the peer when needed.
Let each node signal the driver node when finished.
With this we don't need to go through the daemon to schedule the
graph, nodes will simply activate eachother. We only go to the
server when there is a server node to schedule.
Keep stats about the state of each node and the time it was
triggered, running and finished.
Allocate a per node a piece of shared memory where we place the
activation structure with the graph state and io_position.
We can then give this info to nodes so that they can get the position
in the graph directly but also later, activate the next node in
the graph.
Make the code to export objects more generic. Make it possible for
modules to register a type to export.
Make the client-node also able to export plain spa_nodes.
Let the remote signal the global of the exported object if any. We can
then remote the (unused) remote_id from the proxy.
