Add background migration to archive job traces
Description
In Gitlab %10.6, we prepared a rake task to archive job traces (FYI, We used this script to migrate files from file storage to object storage), however, on-prem instances still has not archived job traces. Users can do this by running rake gitlab:traces:archive
manually, but ideally this should be done by background migrations to make it happen automatically.
%11.0 is the good timing to arhicve this.