Fix missing `ci_cd_settings` relation on project creation

What does this MR do and why?

Contributes to #421050 (closed)

Problem

Relation ci_cd_settings is automatically created for every new project. But it only works if this relation was not touched during project creation flow.

group_runners_enabled field is delegated to ci_cd_settings. When user passes group_runners_enabled to the Projects::CreateService, it initializes ci_cd_settings relation with a nil value. Because of that, when the project is saved this relation doesn't create a record in ci_cd_settings table.

Solution

Explicitly build an association for ci_cd_settings if it's missing.

MR acceptance checklist

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How to set up and validate locally

1. See steps to reproduce: #421050 (closed)