Reverse edge in face sweep instead of edge sweep

From the perspective of the edge sweep operation, there is no such thing
as a negative direction. This is only relevant to the face sweep, so it
makes more sense to do it there.

And in fact, the edge sweep operation can't even decide whether it
*should* reverse. The way the decision is made right now is incorrect:
#990

crates/fj-kernel/src/algorithms/sweep/edge.rs

@@ -17,12 +17,6 @@ impl Sweep for (Edge, Color) {
         let (edge, color) = self;
         let path = path.into();
 
-        let edge = if path.is_negative_direction() {
-            edge.reverse_including_curve()
-        } else {
-            edge
-        };
-
         let surface = edge.curve().sweep(path);
 
         // We can't use the edge we're sweeping from as the bottom edge, as that

crates/fj-kernel/src/algorithms/sweep/face.rs

@@ -22,6 +22,11 @@ impl Sweep for Face {
 
         for cycle in self.all_cycles() {
             for &edge in cycle.edges() {
+                let edge = if path.is_negative_direction() {
+                    edge.reverse_including_curve()
+                } else {
+                    edge
+                };
                 let face = (edge, self.color()).sweep(path);
                 faces.push(face);
             }