It turns out that the real (not mocked) implementation of JobTicket creation
is already required now for this planned (mock)Dispatcher setup;
moreover, this real implementation turns out to be almost identical
to the mock implementation written recently -- just nested structure
of prerequiste JobTickets need to be changed into a similar structur
of ExitNodes
-- as an aside: rearrange various tests to be more in-line
with the envisioned architecture of playback and engine
several years ago, it seemed like a good idea to incorporate
the link between nominal time and wall-clock time into a dedicated
anchor point, which also regulates the continued frame planning.
But it turned out that such a design mixes up several concepts
and introduces confusion regarding the meaning of "real time"
- latency can not be reasonably defined for a whole planning chunk
- skipping or sliding due to missed deadlines can not reasonably handled
within such an abstract entity; it must be handled rather at the
level of a playback process
- linking the frame grid generation directly to a planning chunk
undercuts the possible abstraction of a planning pipeline
