Make resources fetched via resources.Get and similar language agnostic

Make resources fetched via resources.Get and similar language agnostic

With the newly released Hugo Pipes, resources fetched and processed via `resources.Get` and similar was published to the relevant language sub folder when in multilingual mode.

The thought behind that was maximum flexibility with support for `assetDir` per language.

In practice this was a bad idea:

* You get duplication of identical content, with added processing time
* You end up with path issues that seem to be hard to find a way around (`@fa-font-path` is one example)

This commit changes that. Now there is only one `assetDir` and if you, as one example, need to generate a CSS per langugage, you need to set the paths yourself.

Fixes #5017