`options` Accepts Query

[parkervg]

Did a little rework so that the options argument can be one of 3 things:

• {tablename}::{columnname} string
• String of ; separated values
• Another BlendSQL query which returns a set of values

For example, the following is now possible:

SELECT DISTINCT merchant FROM transactions WHERE
merchant = {{
    LLMQA(
        'Which merchant is most likely to sell italian food?',
        (SELECT merchant FROM transactions),
        options=(SELECT merchant FROM transactions WHERE amount > 100)
    )
}}

The selected merchant will now be restricted to the subset where amount > 100.

I added test_query_options_arg in test_single_table_blendsql.py for this change.