Merge branch...

Merge branch '497253-move-contents-of-mixins-to-class-where-it-is-used-if-it-is-only-used-once-2-part-1' into 'master' 

Move contents of Mixins to class where it is used if it is only used once - Part 1

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/167852



Merged-by: Savas Vedova <svedova@gitlab.com>
Approved-by: Eduardo Bonet <ebonet@gitlab.com>
Approved-by: Savas Vedova <svedova@gitlab.com>
Co-authored-by: James Rushford <jrushford@gitlab.com>