[moves] Mark generated moves with square brackets

Update the implementation of Display for GeneratedMove to wrap the ply in [ ].

moves/src/generators.rs

@@ -34,7 +34,7 @@ impl GeneratedMove {
 
 impl std::fmt::Display for GeneratedMove {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-        self.ply.fmt(f)
+        write!(f, "[{}]", self.ply)
     }
 }