Various useful helpers (#41684)

Split out of #41543.

These don't make too much sense on their own, but they also don't really
hurt. They are preparation for #41543, but in order to make things
either to review I split these four commits out, since they are not
directly part of what the PR shall achieve

diff --cc src/basic/string-util.c
Simple merge

diff --cc src/basic/string-util.h
Simple merge