utils: Convert fs error messages from multibyte to utf-8
Summary: Backport of core PR14192.
Test Plan:
ninja check check-functional
Run the Windows Gitian build.
On Windows:
./bitcoin-qt.exe -regtest -wallet=???
Before:
After:
Reviewers: #bitcoin_abc, jasonbcox
Reviewed By: #bitcoin_abc, jasonbcox
Differential Revision: https://reviews.bitcoinabc.org/D5538