Propagate orderings through struct-producing projections #21217

Is your feature request related to a problem or challenge?

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, there is 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.

Describe the solution you'd like

Add 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.

Describe alternatives you've considered

No response

Additional context

No response