numfmt: --format width accounting diverges from GNU for multi-byte --suffix #11937 fix

[Devel08]

This PR closes #11937.
Previously, uutils numfmt treated non-ascii characters as a few characters (equal to the bytes' count), there character counts were considered when using width in the precision flag.
for example 🔗 was treated as f0 9f 94 97 (4 characters). It will now treat it as a single character, just as GNU numfmt does.

[github-actions]

GNU testsuite comparison:

Skip an intermittent issue tests/cut/bounded-memory (fails in this run but passes in the 'main' branch)
Skip an intermittent issue tests/date/date-locale-hour (fails in this run but passes in the 'main' branch)
Skip an intermittent issue tests/pr/bounded-memory (fails in this run but passes in the 'main' branch)
Note: The gnu test tests/misc/write-errors was skipped on 'main' but is now failing.

[cakebaker]

Thanks!