Temporary disable `GC.compact` to avoid segfaults

What does this MR do?

After enabling nakayoshi_fork config for Puma, which performs GC.compact as a part of pre-forking preparation, we discovered that multiple gems, such as Hamlit , oj and thift do not support GC compacting which leads to SEGFAULT in webserver processes.

An additional complication is that these failures are very random and only visible rarely, which makes them almost undetectable in CI or local envs.

To avoid the issue, our short term solution is:

• Disable nakayoshi_fork in production entirely: #323555 (comment 523188172) . This includes entire pre-forking routine, including 4 GC cycles and GC compacting, as they are controlled via a single nakayoshi_fork Puma config in puma.rb
• Next, we want to disable the GC compacting only, but keep the 4 GC cycles preceding the compacting in Puma's nakayoshi_fork
• After that we may want to revert https://ops.gitlab.net/gitlab-cookbooks/chef-repo/-/merge_requests/5121 and gitlab-com/gl-infra/k8s-workloads/gitlab-com!719 (merged)
• Next step is to develop a long-term solution, how and when we could advance with GC.compact, will be in a separate issue

Why monkey patching

This is a compromise.

To achieve a similar effect via monkey patch, we should do:

• Open 4 MRs (GitLab, GDK, CNG, Omnibus) which removes nakayoshi_fork line from config/puma.rb entirely
• Reintroduce https://github.com/ko1/nakayoshi_fork into GitLab repo again (5th MR)
• Additionally, we will need similar 5 MRs to return back this config after finding a better solution to deal with segfaults or catch them during the CI/testing phase

Having a monkey patch, only 1 MR is needed.

Does this MR meet the acceptance criteria?

Conformity

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Availability and Testing

How I tested locally:

• restarted GDK
• Noticed the message (below) in logs:

2021-03-09_09:49:13.55571 rails-web             : {"timestamp":"2021-03-09T09:49:13.555Z","pid":57162,"message":"! Compacting..."}
2021-03-09_09:49:13.55575 rails-web             : Note: GC compacting is currently disabled. Refer to `config/initializers_before_autoloader/003_gc_compact.rb` for details.
2021-03-09_09:49:13.55577 rails-web             : {"timestamp":"2021-03-09T09:49:13.555Z","pid":57162,"message":"! Friendly fork preparation complete."}

Security

N/A

Related to #323555 (closed)