[noetic-devel] Add voxel grid filter and support for processing points with masks

PR Type

Addition of voxel grid filter in related to https://github.com/Alpaca-zip/ultralytics_ros/issues/34.
Add support for processing points with masks.
Fix to fuse models to reduce yolo start-up time.
Add parameter to enable gpu device to be specified in related to issue https://github.com/Alpaca-zip/ultralytics_ros/issues/33.
Changed the use of the classes parameter.
Changed the type of messages that tracker_node publishes.
Add PR template.

The type of messages published by tracker_node has been changed as follows.
- ~result_topic
```
std_msgs/Header header
vision_msgs/Detection2DArray detections
sensor_msgs/Image[] masks
```
- ~result_image_topic(sensor_msgs/Image)
If you are using segmentation(e.g. yolov8m-seg.pt), tracker_with_cloud_node uses the mask image in project cloud.

tracker_node tracker_with_cloud_node
If you want to run yolo with a specific class id, modify the launch file as follows.
```
<arg name="classes" default="[0, 1]"/> 
```
If you want to specify the device to be used by yolo (e.g. cpu or cuda:0), modify the launch file as follows.
```
<arg name="device" default="cpu"/> 
```
```
<arg name="device" default="0"/> 
```