add error for prefixed non multi units

[andrewgsavage]

• Closes Problems when converting values with offset and prefixes #1504 Raise exception on prefixed non-multiplicative units. #1754 Temperature conversion issue #1995
• Executed pre-commit run --all-files with no errors
• The change is fully covered by automated unit tests
• Documented in docs/ as appropriate
• Added an entry to the CHANGES file

[codspeed-hq]

CodSpeed Performance Report

Merging #1998 will not alter performance

_{Comparing andrewgsavage:multi (e8f11b5) with master (9972e60)}

Summary

✅ 437 untouched benchmarks