Behavior tree retry node: support retrying a fixed number of times

libs/util/include/psemek/util/behavior_tree.hpp

@@ -565,13 +565,17 @@ namespace psemek::util
 		struct retry
 		{
 			Child child;
+			std::optional<int> max_count;
+			int count;
 
-			retry(Child child)
+			retry(Child child, std::optional<int> max_count = std::nullopt)
 				: child(std::move(child))
+				, max_count(max_count)
 			{}
 
 			void start(Args ... args)
 			{
+				count = 0;
 				child.start(args...);
 			}
 
@@ -584,7 +588,10 @@ namespace psemek::util
 						return finished{true};
 					else
 					{
-						start(args...);
+						++count;
+						if (max_count && count == *max_count)
+							return finished{false};
+						child.start(args...);
 						return running{};
 					}
 				}