When explicit JOIN syntax is used the from list will contain a
JoinExpr instead of a list of RangeTblRef which was not detected
properly by cagg_validate_query. This patch adds a check for
RangeTblRef to the validation code.
Add indexes for materialization table created by continuous aggregates.
This behavior can be turned on/off by using timescaledb.create_group_indexes parameter
of the WITH clause when the continuous agg is created.
Tests include:
1. UPDATEs get logged to the invalidation log.
2. the invalidation log is not written to on ABORT.
3. custom time-partitioning functions are not supported
(also updates error message for this case).
