Add limits to job logs

What does this MR do?

Related to https://gitlab.com/gitlab-org/gitlab/-/issues/276192

It adds a limit of 100 megabytes to the job logs.

Script to generate a large trace:

image: ruby:alpine

test:
  script:
    - 'ruby -rsecurerandom -e "1000000000.times { |i| id = i.to_s.rjust(10, \"0\"); puts \"#{id}: #{SecureRandom.hex}\" }"'

Migration output

VERSION=20210702124842 bin/rails db:migrate:redo
== 20210702124842 AddCiJobTraceSizeToPlanLimits: reverting ====================
-- remove_column(:plan_limits, :ci_jobs_trace_size_limit, :integer, {:default=>100, :null=>false})
   -> 0.0092s
== 20210702124842 AddCiJobTraceSizeToPlanLimits: reverted (0.0115s) ===========

== 20210702124842 AddCiJobTraceSizeToPlanLimits: migrating ====================
-- add_column(:plan_limits, :ci_jobs_trace_size_limit, :integer, {:default=>100, :null=>false})
   -> 0.0055s
== 20210702124842 AddCiJobTraceSizeToPlanLimits: migrated (0.0056s) ===========

Screenshots (strongly suggested)

Does this MR meet the acceptance criteria?

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• This change is backwards compatible across updates, or this does not apply.

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