Scope `ci_include_components` feature flag to Namespace

What does this MR do and why?

Related to [Feature Flag] Enable `ci_include_components` (#390646 - closed)

In this MR I simply change the actor of the feature flag from Project to Namespace ensuring that we always use the root_namespace.

This makes is easier to enable the feature for an entire namespace/organization than enabling it for each project. By enabling the FF once we can have:

• a namespace defining a components repository and testing it in its own .gitlab-ci.yml.
• another project in the same namespace using a component from that repository.

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