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/assembly.rs

@@ -205,6 +205,7 @@ impl FeatureKind {
     /// Map the feature's world geometry (points, directions, explicit planes) by `m`.
     pub fn transform_geometry(&mut self, m: &Mat) {
         use crate::feature_geometry::Geo;
+        use crate::walk::Walk;
         self.walk_geometry_mut(&mut |g| match g {
             Geo::Pick(p) | Geo::Pos(p) => *p = apply_point(m, *p),
             Geo::Dir(v) => *v = apply_vector(m, *v),