Profile code included in a bounded context of `Gitlab::Ci::Config`

Description

It might be a good idea to profile the code included within GitLab::Ci::Config class from the gitlab-ce~27312481 perspective. This class is a composite, and we do quite a few back-and-forth round trips to compose it.

It is possible that we can improve performance of creating new pipelines with simple changes there.

Creating an issue to not forget about it.