[topology] adding 'Neighbor::AddressMatcher' (#5354)

This commit adds new a type `Neighbor::AddressMactehr` which is used
to filter and find a neighbor (child/router) with a given MAC address
matching a given `Neighbor::StateFilter`. This new type helps simplify
related code in `ChildTable`/`RouterTbale`.

tests/unit/test_child_table.cpp

@@ -96,9 +96,17 @@ static bool StateMatchesFilter(Child::State aState, Child::StateFilter aFilter)
         rval = child.IsStateValidOrAttaching();
         break;
 
+    case Child::kInStateInvalid:
+        rval = child.IsStateInvalid();
+        break;
+
     case Child::kInStateAnyExceptValidOrRestoring:
         rval = !child.IsStateValidOrRestoring();
         break;
+
+    case Child::kInStateAny:
+        rval = true;
+        break;
     }
 
     return rval;