Summary:
Column conversions involve changes to metadata tables such as
_grist_Tables_column. When fetched (from GranularAccess), ExpandedQuery used to
fail with 'table not found' because there is no metadata for metadata tables.
This diff limits the need for metadata in ExpandedQuery to when it's actually
needed (to implmement some formulas for on-demand tables), which no longer
interferes with GranularAccess.
Test Plan: Added a test case that reproduces the issue before the fix.
Reviewers: paulfitz
Reviewed By: paulfitz
Differential Revision: https://phab.getgrist.com/D2729