Use Puma `nakayoshi_fork`

⚠ I'd prefer to sync the merge of the listed 4 MRs. It shouldn't block the review/approvals though 🙂

What does this MR do?

• Relates to gitlab#288042 (closed).
• Enables nakayoshi_fork by default
• Uses ENV var for better control of the option
• Removes if defined check which was needed prior to Puma 5.1 migration for compatibility (gitlab!48897 (merged), gitlab#292918 (closed)) : we decided to keep it for a few more release cycles

Related issues

gitlab#288042 (closed)
gitlab#292918 (closed)

All config-related MRs for this change (for cross-reference):

• gitlab!51467 (merged)
• !4914 (merged)
• gitlab-org/build/CNG!581 (merged)
• gitlab-development-kit!1758 (merged)

Checklist

See Definition of done.

For anything in this list which will not be completed, please provide a reason in the MR discussion

Required

• Merge Request Title, and Description are up to date, accurate, and descriptive
• MR targeting the appropriate branch
• MR has a green pipeline on GitLab.com
• [-] Pipeline is green on dev.gitlab.org if the change is touching anything besides documentation or internal cookbooks – not sure what it means / how to trigger it?
• trigger-package has a green pipeline running against latest commit

Expected (please provide an explanation if not completing)

• Test plan indicating conditions for success has been posted and passes - it should be enough to check that the webserver is starting without any issues
• Documentation created/updated
• [-] Tests added
• [-] Integration tests added to GitLab QA
• [-] Equivalent MR/issue for the GitLab Chart opened - I didn't find that config in charts