Group by Alias

[jychen7]

Describe the bug
#110 suggests we can group by alias, however, I modify the existing test case select_simple_aggregate_with_groupby_with_aliases a bit, then it fails

To Reproduce

SELECT state AS a, MIN(age) AS b FROM person GROUP BY state

shows correct answer

SELECT state AS a, MIN(age) AS b FROM person GROUP BY a

raises error Plan("Projection references non-aggregate values")

Expected behavior

SELECT state AS a, MIN(age) AS b FROM person GROUP BY state

SELECT state AS a, MIN(age) AS b FROM person GROUP BY a

returns same answer

[jychen7]

I think we could resolve_aliases_to_exprs for select.group_by
similar to
datafusion/blob/e86ad26a678a32e2743bc031ae5cb81e6931a231/datafusion/src/sql/planner.rs#L563-L566

However, as a rust learner, I am still on the way struggling the rust typing system when deal with the array mapping

[alamb]

Thanks @jychen7 -- the expected behavior looks correct here 👍 Let us know if you need any help with the Rust