cmake: Fix diverging prefix padding for OBS status outputs

Status output related to OBS configuration is prefixed with the string
"OBS" and added padding for enabled and disabled features. This padding
was not aligned between platforms.

By moving the padding and prefix decoration into its own function,
both elements are controlled in a single place. CMake scripts were
changed to use this new function `obs_status` instead of using CMake's
`message` function directly.

UI/CMakeLists.txt

@@ -2,7 +2,7 @@ add_subdirectory(obs-frontend-api)
 
 option(ENABLE_UI "Enable building with UI (requires Qt)" ON)
 if(NOT ENABLE_UI)
-  message(STATUS "OBS:  DISABLED   OBS UI")
+  obs_status(DISABLED "OBS UI")
   return()
 endif()