[backport#16224 2/5] Make ThreadSafe{MessageBox|Question} bilingual
Summary:
This PR:
- makes GUI error messages bilingual: user's native language + untranslated (i.e. English)
- insures that only untranslated messages are written to the debug log file and to stderr (that is not the case on master).
Backport of Core PR16224 - part 2 of 5
https://github.com/bitcoin/bitcoin/pull/16224/commits/917ca93553917251e0fd59717a347c63cdfd8a14
Depends on D7985
Test Plan: ninja && ninja check
Reviewers: O1 Bitcoin ABC, #bitcoin_abc, deadalnix
Reviewed By: O1 Bitcoin ABC, #bitcoin_abc, deadalnix
Differential Revision: https://reviews.bitcoinabc.org/D7986