Support Multi-Column Producing Function Implementation

[Ted-Jiang]

I think we will need to introduce a new type of function to cover inline since it is not a scalar function.

I don't have a good name for it yet but I think we need something like this?

pub type MultiColumnProducingFunctionImplementation =
    Arc<dyn Fn(&[ColumnarValue]) -> Result<Vec<ColumnarValue>> + Send + Sync>;

Originally posted by @andygrove in #2330 (comment)

[Ted-Jiang]

I thinks we can call it TableFunctionImplementation
https://docs.snowflake.com/en/sql-reference/functions-table.html

[alamb]

I think a multiple column table function is different than a "table function"

A table function returns (potentially) multiple columns and rows where as I think this ticket is just talking about returning multiple columns.

The natural thing in my mind for this usecase would be to return a single column of DataType::Struct (or DataType::List)

However DataFusion's support for such compound datatypes is in need of work -- see #2326