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/8ba5ae7a-5ae5-4eab-9fcc-5dd4fe3abf89.json

@@ -7,7 +7,7 @@
     {
       "type": "launch",
       "parameters": {
-        "command": "vlc"
+        "command": "VLC_VERBOSE=-1 vlc"
       }
     },
     {