Remove NO_EDITOR/NO_CUSTOM_LEVELS, disable editor on Steam Deck

This commit removes the `NO_EDITOR` and `NO_CUSTOM_LEVELS` defines,
which cleans up the code a lot, and they weren't really needed anyways.

This commit also disables the editor on the Steam Deck, and adds a
program argument to re-enable the editor, `-enable-editor`.

desktop_version/src/LocalizationStorage.cpp

@@ -947,10 +947,9 @@ static void loadtext_roomnames(bool custom_level)
             {
                 continue;
             }
-#if !defined(NO_CUSTOM_LEVELS)
+
             const RoomProperty* const room = cl.getroomprop(x, y);
             if (SDL_strcmp(original_roomname, room->roomname.c_str()) != 0)
-#endif
             {
                 continue;
             }