The test split matches PR #8920, so the utility files and tests files
are once again to 1-1. The string changes continues what was started in
PR #11093.
Inspired by
010ff57ebb
From the original PR:
> We do not have any of these warnings appearing at the moment, but
> it seems like a good idea to enable [[nodiscard]] checking anyway.
> Once we start introducing more functions with must-use conditions we will
> need such checking, and the rust stdlib has proven them very useful.
