Add Scalar to ScalarValue Nested Type

I know I'm coming in a little late, but have we considered instead making the type `Scalar>`? ([Scalar being the one in arrow-rs](https://docs.rs/arrow/latest/arrow/array/struct.Scalar.html)) This would enforce that the length is 1, which might be nice. I could also understand if that makes it too awkward to work with.

Nested Type including, List, LargeList, FixedSizeList, Struct

_Originally posted by @wjones127 in https://github.com/apache/arrow-datafusion/pull/8562#discussion_r1443856458_

File a ticket to trace this issue

Better start it after https://github.com/apache/arrow-datafusion/issues/7835