fix R-level fr-FR translation

[cregouby]

After some exchange with Philippe Grosjean during the French Rencontre R 2024,
I finally got the correct way to wrap R-level messages so that they get translated.

> withr::with_language(lang = "fr",
+                      torch_scalar_tensor(torch_randn(8, 2, 7))
+ )
Error in `value_error()` at torch/R/creation-ops.R:380:5:
! les valeurs doivent être de longueur 1
Run `rlang::last_trace()` to see where the error occurred.
Called from: signal_abort(cnd, .file)
Browse[1]> 
> 

Note
Cpp-level translation is

• missing (no collection of the messages in po(t) files yet)
• not working as it requires wrapping all C/C++ level "messages" into _("message") but gettext does not get the one in Rcpp::stop(). I'll make it explicit in a issue.

[dfalbel]

@cregouby I rebased the PR. Some test cases are failing, and they seem related to this PR.

[cregouby]

Oh ! Sorry for that.
Please give me some time to have a deeper look...

[dfalbel]

No worries, let me know if you want me to take a look too!

[dfalbel]

I also just added you as a collaborator so you don't need to wait for me to approve and run your PR's.

[cregouby]

Thanks, I feel honored !