Make edge metrics strongly typed (#6421)

This change takes the existing typedefs for weight, duration and
distance, and makes them proper types, using the existing Alias
functionality.

Primarily this is to prevent bugs where the metrics are switched,
but it also adds additional documentation. For example, it now
makes it clear (despite the naming of variables) that most of the
trip algorithm is running on the duration metric.

I've not made any changes to the casts performed between metrics
and numeric types, they now just more explicit.

include/customizer/cell_customizer.hpp

@@ -61,7 +61,7 @@ class CellCustomizer
                 }
             }
             heap.Clear();
-            heap.Insert(source, 0, {false, 0, 0});
+            heap.Insert(source, {0}, {false, {0}, {0}});
 
             // explore search space
             while (!heap.Empty() && !destinations_set.empty())
@@ -216,12 +216,11 @@ class CellCustomizer
                                                     partition.GetCell(level - 1, to)))
             {
                 const EdgeWeight to_weight = weight + data.weight;
-                const EdgeDuration to_duration = duration + data.duration;
+                const EdgeDuration to_duration = duration + to_alias<EdgeDuration>(data.duration);
                 const EdgeDistance to_distance = distance + data.distance;
                 if (!heap.WasInserted(to))
                 {
-                    heap.Insert(
-                        to, to_weight, {false, duration + data.duration, distance + data.distance});
+                    heap.Insert(to, to_weight, {false, to_duration, to_distance});
                 }
                 else if (std::tie(to_weight, to_duration, to_distance) <
                          std::tie(

include/customizer/edge_based_graph.hpp

@@ -97,7 +97,7 @@ class MultiLevelGraph : public partitioner::MultiLevelGraph<EdgeDataT, Ownership
 
     EdgeWeight GetNodeWeight(NodeID node) const { return node_weights[node]; }
 
-    EdgeWeight GetNodeDuration(NodeID node) const { return node_durations[node]; }
+    EdgeDuration GetNodeDuration(NodeID node) const { return node_durations[node]; }
 
     EdgeDistance GetNodeDistance(NodeID node) const { return node_distances[node]; }