Add more tests for mixed-format tables, including parquet

We only have a single very basic table with mixed formats that I can see. It would be good to have a larger table that includes parquet, so we can exercise some of the more interesting memory reservation code paths. I think the requirements are:

• Files of at least multiple MBs in size
• Includes Parquet and at least one row-based format
• Ideally a mix of different file and partition sizes

We want queries that exercise "interesting" code paths:

• Many columns returned: select * from table.
• Single column returned
• No columns returned - e.g. select count
• Selective scan with predicates