Instead of using static elements, use a dynamically generated DBSP-
circuit to keep views.
The DBSP circuit is generated from the logical plan, which only supports
enough for us to generate the DBSP circuit at the moment.
The state of the view is still kept inside the IncrementalView, instead
of materialized at the operator level. As a consequence, this still
depends on us always populating the view at startup. Fixing this is the
next step.
Closes#2815
ca7f1002b4