Being the good boyscouts, but mainly because of [the comment in the
review](https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/12378#note_33302115)
the words used for classes and variables are changed to not use builds
anymore.

Achieved by using another table, which both has better indexes and
is smaller. Now the data provided for the user is more valueable too.

Close #32994