stretch_camera_streams_check.py should check if X server running

[hello-lamsey]

Description

The stretch_camera_streams_check.py script in stretch_body_tools throws a qt exception when running the script in an SSH session. I use this script to check if my d405 / d435 are streaming properly without needing to check the output images themselves. The script should check if an X server is running in the session before attempting to render.

Steps to Recreate

1. SSH into the robot
2. Run stretch_camera_streams_check.py

Expected output:

hello-robot@stretch-se3-3043:~$ stretch_camera_streams_check.py 
For use with S T R E T C H (R) from Hello Robot Inc.
---------------------------------------------------------------------

cv2.__version__ = 4.9.0
sys.version = 3.10.12 (main, Nov 20 2023, 15:14:05) [GCC 11.4.0]

D405 Stream Settings:
 D405_COLOR_SIZE=[640, 480]
 D405_DEPTH_SIZE=[640, 480]
 FPS=15
D435i Stream Settings:
 D435I_COLOR_SIZE=[640, 480]
 D435I_DEPTH_SIZE=[640, 480]
 FPS=30
Navigation Camera Stream Settings:
 UVC_COLOR_SIZE=[1280, 720]
 FPS=30
qt.qpa.xcb: could not connect to display 
qt.qpa.plugin: Could not load the Qt platform plugin "xcb" in "/home/hello-robot/.local/lib/python3.10/site-packages/cv2/qt/plugins" even though it was found.
This application failed to start because no Qt platform plugin could be initialized. Reinstalling the application may fix this problem.

Available platform plugins are: xcb.

Aborted (core dumped)