Add a convenience node to visualize compressed images

[hello-amal]

Description

Since RVIZ2 does not currently allow rendering compressed images, this PR adds a convenience node to do so.

Testing

• [x] Connect to the Stretch GUI (e.g., via HDMI cable, Moonlight, etc.)
• [x] Launch the web app: colcon_cd stretch_web_teleop; ./launch_interface.sh
• [x] Run this node: ros2 run stretch_web_teleop compressed_image_visualizer.py --ros-args --remap /camera/color/image_raw/compressed:=/gripper_camera/image_raw/cropped/compressed
• [x] Verify that it renders properly and is real-time.
• [x] Terminate the node (Ctrl-C), verify it cleanly terminates.

[hello-amal]

I think Python's garbage collector should handle it (I haven't experienced any issues as a result of not calling cv2.destroyAllWindows()), but I added it for good measure and re-ran the tests.