Add URDF and XACRO files for iiwa7 robot and tool patron

- Created iiwa7_gazebo.urdf to define the iiwa7 robot model with detailed links, joints, and Gazebo integration.
- Introduced patron.xacro for the tool patron, including its inertial properties, visual representation, and collision geometry.

src/iiwa_description/urdf/iiwa7_digital.urdf.xacro

@@ -13,7 +13,9 @@
     <xacro:include filename="$(find iiwa_description)/urdf/links.xacro"/>
     <xacro:include filename="$(find iiwa_description)/urdf/joints.xacro"/>
 
-    <xacro:include filename="$(find iiwa_description)/urdf/gripper/gripper.xacro"/>
+    <!-- <xacro:include filename="$(find iiwa_description)/urdf/gripper/gripper.xacro"/> -->
+    <xacro:include filename="$(find iiwa_description)/urdf/tools/patron.xacro"/>
+
 
     <webots>
         <plugin type="webots_ros2_control::Ros2Control"/>