Phase 2: make sort pushdown support exact mode which can support sort elimination when ordering is guaranteed #19329

//! ## Current capabilities (Phase 1)
//!
//! - Reverse scan optimization: when required sort is the reverse of the data source's
//!   natural ordering, enable reverse scanning (reading row groups in reverse order)
//! - Supports prefix matching: if data has ordering [A DESC, B ASC] and query needs
//!   [A ASC], reversing gives [A ASC, B DESC] which satisfies the requirement
//!
//! ## Future enhancements (Phase 2)
//!
//! - File reordering based on statistics
//! - Return `Exact` when files are known to be perfectly sorted
//! - Complete Sort elimination when ordering is guaranteed