Remove unused and racy "used" param from streamformatter

Also tests written
Docker-DCO-1.1-Signed-off-by: Alexandr Morozov <lk4d4math@gmail.com> (github: LK4D4)
Merge pull request #6150 from LK4D4/remove_used_from_streamformatter

Remove unused and racy "used" param from streamformatter