wallet: Avoid translating RPC errors when loading wallets

Summary:
Common errors and warnings should be translated when displayed in the
GUI, but not translated when displayed elsewhere. The wallet method
CreateWalletFromFile does not know its caller, so this commit changes it
to return a bilingual_str to the caller.

This is a partial backport of Core PR18699 : https://github.com/bitcoin/bitcoin/pull/18699/commits/fae51a5c6f4270a1088e6295b10a8cc45988ae46

Depends on D7699

Test Plan:

ninja all check-all

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Subscribers: Fabien

Differential Revision: https://reviews.bitcoinabc.org/D7701