Modify VLC launch command and fullscreen detection

- Add VLC_VERBOSE=-1 to suppress verbose logging in VLC launch commands across multiple example files
- Update is_vlc_fullscreen function to handle cases where screen size or window size is None
- Improve robustness of VLC-related metrics and example configurations

evaluation_examples/examples/vlc/386dbd0e-0241-4a0a-b6a2-6704fba26b1c.json

@@ -30,6 +30,7 @@
       "type": "launch",
       "parameters": {
         "command": [
+          "VLC_VERBOSE=-1",
           "vlc",
           "--start-time=10",
           "/home/user/Desktop/Colorful-Flowers.mp3"