Migrate away ci_builds.trace
I did check on GitLab.com how much data is stored in
ci_builds.trace column. This was used when GitLab CI was still separate product. We then moved to storing traces on disk. According to my queries, it is:
$ Ci::Build.where.not(trace: nil).count => 87636 $ Ci::Build.where.not(trace: nil).pluck('sum(octet_length(trace))') => 
It is over 5.5GB, on average over 60k per build.
We should prepare Background Migration to move that to disk.