libobs,docs: Improve failed module loading logging

- Avoid putting libs (like CEF) in the plugins load failure message.
- Consider obsolete macOS obs-browser plugin fail as a hardcoded skip.

libobs/obs-defs.h

@@ -31,6 +31,7 @@
 #define MODULE_FILE_NOT_FOUND -2
 #define MODULE_MISSING_EXPORTS -3
 #define MODULE_INCOMPATIBLE_VER -4
+#define MODULE_HARDCODED_SKIP -5
 
 #define OBS_OUTPUT_SUCCESS 0
 #define OBS_OUTPUT_BAD_PATH -1