Use arrow Date32 type in query engine

[Taepper]

After a TableScan, we expand our internal Date32 type to a string. This can be avoided and we should just use arrow's provided Date32 type

[Taepper]

This would lead to breaking behavior for the arrow interface (the returned batches will contain date32 arrays instead of string). We could add date32 -> string conversion like we do the ZstdDecompress instead, but this touches the code that has been changed in #1182