Move generated translation files into res://.godot/translations

[aaronfranke]

Follow up to #38607. Implements and closes godotengine/godot-proposals#1812.

This moves the generated .translation files into a subfolder of res://.godot called res://.godot/translations (defined as a constant: TranslationServer::TRANSLATION_FILES_PATH). These files are generated and don't need to be committed, which is the goal of the res://.godot folder.

Note that projects need to be manually updated, since project.godot explicitly references the translation files. For example, the translation demo contains res://text.en.translation in project.godot.

The simplest solution was to make the contents of this folder replicate the folder structure of the project, so a file res://subfolder/text.csv gets imported as res://.godot/translations/subfolder/text.en.translation etc. Because the generated translation files have to be referenced explicitly, I think this is actually really nice.

Another question is what to call this folder. I think "translation" is nice because it contains .translation files, but one could make the argument that this folder should be called "translations" instead.

[akien-mga]

This might not work anymore, right() was changed in #36180. This should use the clearer substr().

[aaronfranke]

I updated the PR to use substr. I also tried testing it again, and I wasn't able to get the translation demo to work either with or without this PR. For now I will assume that this specific code still works because it worked when I made the PR.

[akien-mga]

For the record, the reason I haven't merged this yet is that I'm not sure that translation files can be considered as files which shouldn't be version controlled. I need to double check that.

They do get generated from CSVs, but I'm not sure that they get automatically generated or updated, and they depend on enabling specific languages in Project Settings, etc. It's not as clear cut as textures or samples.

[akien-mga]

Finally got to test this, and indeed as I feared it doesn't seem to work with the actual translation workflow. Did you try to port the gui/translation demo using it?

The CSV gets imported as .translation files, and then the translation files need to be added to the Localization tab in the Project Settings:

With this change users would need to go find them in .godot/translations/ which is hidden.

[aaronfranke]

@akien-mga Is there a way that we can have users select the original CSV and have Godot automatically get the translation file?

[mhilbrunner]

@akien-mga See above :P