Replace factory_girl_rails with factory_bot_rails

See merge request gitlab-org/gitlab-ce!15919

I've followed the [upgrade guide](https://github.com/thoughtbot/factory_bot/blob/4-9-0-stable/UPGRADE_FROM_FACTORY_GIRL.md) and ran these two commands:

```
grep -e FactoryGirl **/*.rake **/*.rb -s -l | xargs sed -i "" "s|FactoryGirl|FactoryBot|"
grep -e factory_girl **/*.rake **/*.rb -s -l | xargs sed -i "" "s|factory_girl|factory_bot|"
```

Signed-off-by: Rémy Coutable <remy@rymai.me>

Moving the check out of the general requests, makes sure we don't have
any slowdown in the regular requests.

To keep the process performing this checks small, the check is still
performed inside a unicorn. But that is called from a process running
on the same server.

Because the checks are now done outside normal request, we can have a
simpler failure strategy:

The check is now performed in the background every
`circuitbreaker_check_interval`. Failures are logged in redis. The
failures are reset when the check succeeds. Per check we will try
`circuitbreaker_access_retries` times within
`circuitbreaker_storage_timeout` seconds.

When the number of failures exceeds
`circuitbreaker_failure_count_threshold`, we will block access to the
storage.

After `failure_reset_time` of no checks, we will clear the stored
failures. This could happen when the process that performs the checks
is not running.

* master: (84 commits)
  Migrate Gitlab::Git::Wiki#page to Gitaly
  Load participants async
  Normalize LDAP DN when looking up identity
  Improve the maintenance policy page
  add changelog
  fix spec failure
  Allow promoting project milestones to group milestones
  fix specs
  Be able to bundle gems with newer rubies
  Upgrade Ruby to 2.3.5
  fixed up upload feature after master merge
  fix missing issue assignees
  Migrate Gitlab::Git::Wiki#delete_page to Gitaly
  Enable eslint
  Make `#hashed_storage?` require feature argument
  Adds callback function to inital cluster request
  Fix example typo.
  Upload files through the multi-file editor
  get branch name from the DOM
  Resolve "Convert autosize.js library to be a Yarn managed library"
  ...

Signed-off-by: Rémy Coutable <remy@rymai.me>