Add the missing variables to the finalization view of Continuous
Aggregates and the corresponding columns to the materialization table.
Cover the case of targets that contain Aggref nodes and Var nodes
that are outside of the Aggref nodes at the same time.
Stop rebuilding the Continuous Aggregate view with ALTER MATERIALIZED
VIEW. Attempt to repair the view at post-update time instead, and fail
gracefully if it is not possible to do so without raw hypertable schema
or data modifications.
Stop rebuilding the Continuous Aggregate view when switching realtime
aggregation on and off. Instead, manipulate the User View by either:
1. removing the UNION ALL right-hand side and the WHERE clause when
disabling realtime aggregation
2. adding the Direct View to the right of a UNION ALL operator and
defining WHERE clauses with the relevant watermark checks when
enabling realtime aggregation
Fixes#3898
fab16f3798