feat: Add f_lang function to emulate python f-strings for translations

[stephanegigandet]

Fixes #5961

From a discussion with @alexgarel who suggested python's f-strings.

This is to make it possible to use named variables in translations.
e.g. "blablabla {some_variable} blabla {some_other_variable} bla."

Benefits:

• easier to read/understand than the %s
• function calls are cleaner, no need to remember order of variables (or to change them if we want to rephrase the source string differently)
• makes it possible to have translations where the order of the variable differs by language
• The {variable} is quote close to the ${variable} in perl

For existing strings, I think we can keep the %s for now (unless there's a good reason to change them), so that translators don't have to retranslate them.

For new strings, I think named parameters is better.

[sonarcloud]

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[alexgarel]

👏