迁移了原来的nav2包；新增基于obstacle_scanner构建costmap的nav2，暂未实际测试

src/navigation/cyy_navigation2/bt/navigate_w_replanning_time.xml

@@ -0,0 +1,14 @@
+<!--
+  This Behavior Tree replans the global path periodically at 1 Hz.
+-->
+
+<root main_tree_to_execute="MainTree">
+  <BehaviorTree ID="MainTree">
+    <PipelineSequence name="NavigateWithReplanning">
+      <RateController hz="1.0">
+        <ComputePathToPose goal="{goal}" path="{path}" planner_id="GridBased"/>
+      </RateController>
+      <FollowPath path="{path}"  controller_id="FollowPath"/>
+    </PipelineSequence>
+  </BehaviorTree>
+</root>