refactor(router/astar): Have separate statuses for discarded probes and skipped visits

This is mostly to improve readability. Since we don't check the values
of the continue statuses anywhere anyway, this doesn't result in any
changes to code outside of the router/astar module.

src/router/astar.rs

@@ -139,7 +139,9 @@ where
 #[derive(Debug)]
 pub enum AstarContinueStatus {
     Probing,
+    ProbingButDiscarded,
     Probed,
+    VisitSkipped,
     Visited,
 }
 
@@ -211,7 +213,9 @@ where
                             // No need to add neighbors that we have already reached through a
                             // shorter path than now.
                             if *entry.get() <= next_score {
-                                return Ok(ControlFlow::Continue(AstarContinueStatus::Probed));
+                                return Ok(ControlFlow::Continue(
+                                    AstarContinueStatus::ProbingButDiscarded,
+                                ));
                             }
                             entry.insert(next_score);
                         }
@@ -250,7 +254,7 @@ where
                 // If the node has already been visited with an equal or lower score than
                 // now, then we do not need to re-visit it.
                 if *entry.get() <= estimate_score {
-                    return Ok(ControlFlow::Continue(AstarContinueStatus::Visited));
+                    return Ok(ControlFlow::Continue(AstarContinueStatus::VisitSkipped));
                 }
                 entry.insert(estimate_score);
             }