Feature walks: generate them from field roles with #[derive(Walk)] (#1251)

The three walks over a feature (expressions, references, geometry) are generated from FeatureKind by #[derive(Walk)] in a new proc-macro crate, solidcraft-derive, from #[walk(...)] attributes written next to each field. The hand-written walks in params.rs, feature_refs.rs and feature_geometry.rs are gone; Ruled Surface and Extend have their attributes, and the three golden walk records are unchanged.

Co-authored-by: jijinbei <jijinbei@users.noreply.github.com>

crates/doc/src/lib.rs

@@ -39,6 +39,7 @@ pub mod physical_material;
 mod piece_names;
 mod profile_refs;
 pub mod progress;
+mod walk;
 pub use profile_refs::{capture_profile_selection, profile_selection_indices};
 pub mod plastic;
 pub mod project;