wallet: Avoid translating RPC errors when creating txs

Summary:
Also, mark feebumper bilingual_str as Untranslated

They are technical and have previously not been translated either.
It is questionable whether they can even appear in the GUI.

This is a partial backport of Cor PR18699 : https://github.com/bitcoin/bitcoin/pull/18699/commits/fae7776690c37104d2d4949429c5f84e6a33c576

Test Plan:

ninja all check

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D7703