Fix NoMethodErrors caused by incorrect module loading

What does this MR do?

Ensures that the EE::ProjectsHelper module is prepended to ::ProjectsHelper, and that ::EE::GitlabRoutingHelper includes ::ProjectsHelper (rather than just ::ProjectsHelper, as it was previously)

Are there points in the code the reviewer needs to double check?

I don't have a replication so this is just a guess, but the reasoning seems sound to me.

Why was this MR needed?

Without this, in some circumstances ::ProjectsHelper will not be included in the same place as ::EE::GitlabRoutingHelper, leading to the default_clone_protocol method being undefined and NoMethodError being raised.

Screenshots (if relevant)

Does this MR meet the acceptance criteria?

• Tests added for this feature/bug
• Review
  • Has been reviewed by Backend
• Conform by the merge request performance guides
• Conform by the style guides
• Squashed related commits together

What are the relevant issue numbers?

Closes #3521 (closed)