feat: Propagate orderings through struct-producing projections

[rkrishn7]

When a projection wraps columns into a struct via named_struct (e.g., named_struct('ticker', ticker, ...) AS details), the optimizer loses track of the input column's ordering because ProjectionMapping maps the entire named_struct(...) expression to col("details"). Notably, it has no field-level decomposition, so it can't prove that get_field(details, "ticker") actually preserves the ordering of the input ticker column. This means ORDER BY details['ticker'] will require a SortExec, even when the input is already sorted by ticker.

This PR fixes this by adding ScalarUDFImpl::struct_field_mapping that struct-producing UDFs can implement to declare their field-to-input-arg relationships, which ProjectionMapping then uses to add field-level entries so EquivalenceProperties can propagate orderings through the struct boundary.

[zhuqi-lucas]

LGTM! Clean design and good test coverage.

One issue: is_multiple_of in named_struct.rs:190 is nightly-only (feature(unsigned_is_multiple_of)). This will fail on stable Rust. Should use literal_args.len() % 2 != 0 instead.

[rkrishn7]

LGTM! Clean design and good test coverage.

One issue: is_multiple_of in named_struct.rs:190 is nightly-only (feature(unsigned_is_multiple_of)). This will fail on stable Rust. Should use literal_args.len() % 2 != 0 instead.

Thanks @zhuqi-lucas

usize::is_multiple_of should be stable since 1.87.0 🤔 - https://doc.rust-lang.org/std/primitive.usize.html#method.is_multiple_of

clippy actually instructed me to use is_multiple_of