implement notification coordination

this patch enables coordination of notification agents by splitting
pipelines across agents. a single-worker agent is provided that
skips the overhead of IPC. a multi-worker agent is added that uses
internal queue to redirect samples to correct pipeline.

Implements: blueprint notification-coordination
Change-Id: If8503ee70217025106a188f40a6e4ea8c49a89f4
ensure unique pipeline names

for notification agent coordination, we requeue items based on the
pipeline name. to ensure we have correct queues for pipeline, we
should make sure pipeline names are unique.

Change-Id: I1b3e7cf1206fd11ab7fde15233cdd19416322acc
Implements: blueprint notification-coordination