Add source_query_id and depends_on_filter_id to lotus_dashboard_filters.

A filter with a source_query_id gets its select options from that saved query. A filter with a depends_on_filter_id passes the value of that other filter to its source query, so the options of one filter can depend on the value of another.

Both columns are nullable, and a delete of the referenced query or filter sets them to NULL. Every existing row keeps its static options, so there is no backfill.