Previous bilingual_str tinyformat::format accepted bilingual format strings,
but not bilingual arguments. Extend it to accept both. This is useful when
embedding one translated string inside another translated string, for example:
`strprintf(_("Error: %s"), message)` which would fail previously if `message`
was a bilingual_str.
This is a partial backport of core#27150
https://github.com/bitcoin/bitcoin/pull/27150/commits/3db2874bd71d2391747b7385cabcbfef67218c4c
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refactor: Avoid copy of bilingual_str when formatting, Fix ADL violation
The return type of TranslateArg is std::string, which creates a copy.
Fix this by moving everything into a lambda that takes a reference and
returns a reference.
Also, the format function is called without specifying the namespace it
lives in. Fix this by specifying the namespace. See also:
https://github.com/bitcoin/bitcoin/blob/7a59865793cd710d7d6650a6106ca4e790ced5d3/doc/developer-notes.md#L117-L137.
This is a backport of core#27892