Move tr and tr_n to @GlobalScope

[dalexeev]

godotengine/godot#49149 added the auto_translate property to the Control and Window classes. Now I think set_message_translation has no use cases left (correct me if I'm wrong).

I propose:

1. Move tr and tr_n to @GlobalScope.
2. Remove can_translate_messages and set_message_translation.

Arguments:

1. tr and tr_n can be used in static functions;
2. tr and tr_n will work the same anywhere.

[dalexeev]

Is there any reason why variant utility functions don't support default values?

I wanted to implement this suggestion, but didn't find the right macro in core/variant/variant_utility.cpp.

[dalexeev]

Sorry for the bumping, but I'd like some kind of answer. Yes, you can can easily workaround the restriction on using tr in static functions by using Global.tr (where Global is autoload with Global Variable enabled), but I think this idea makes sense: remove more unnecessary functionality and clean up the API, independence of tr from the state of the object.

[dalexeev]

This cannot be done in 4.x due to backwards compatibility.