Replace GTA_SWITCH macro and use GAMEPAD_MENU

* Replace GTA_SWITCH macro with __SWITCH__ for platform specific stuff and GTA_HANDHELD for the rest (which could be used by other ports)
* Use GAMEPAD_MENU on GTA_HANDHELD, which will replace the usual controller setup (which contains some useless features for handhelds)
* Fix some identation inconsistencies
* Disable PC_PLAYER_CONTROLS on GTA_HANDHELD builds

src/CMakeLists.txt

@@ -149,10 +149,6 @@ endif()
 
 # Build Nintendo Switch binaries
 if(NINTENDO_SWITCH)
-    target_compile_definitions(${EXECUTABLE} PRIVATE
-        GTA_SWITCH
-    )
-
     # Needed for OpenAL-Soft
     target_link_libraries(${EXECUTABLE} PRIVATE
         openal # HACK - something broke with latest cmake