Move audit event types into user directory

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/153939



Merged-by: Suzanne Selhorn <sselhorn@gitlab.com>
Approved-by: Nate Rosandich <nrosandich@gitlab.com>
Approved-by: Nao Hashizume <nhashizume@gitlab.com>
Reviewed-by: Nao Hashizume <nhashizume@gitlab.com>
Co-authored-by: Evan Read <eread@gitlab.com>