Clean up duplicate types in `sql` module

After https://github.com/apache/datafusion/pull/17332, we can make the `datafusion-expr` crate not depend on sqlparser-rs (and copy the relevant types that are needed).

The expr crate should become un-dependent from sqlparser::ast types, so these copies should be the only types we use.

Is there a follow-up issue planned to cleanup these duplicate types?

_Originally posted by @findepi in https://github.com/apache/datafusion/pull/17332#discussion_r2355658394_

Start by reviewing PR 17332 and the datafusion-expr crate's uses of sqlparser::ast types. Identify the copied types that should remain in the expr crate and verify which sqlparser dependency and duplicate definitions can be removed. Done means datafusion-expr no longer depends on sqlparser-rs and uses only its local copies.

Written by the indexing model from the issue text.