Add `Project overview` menu to the project sidebar

What does this MR do?

In this MR, we add the Project Overview menu to the project sidebar refactor. We're basically removing it from the regular HAML view and moving it to the new defined structure for menus.

Screenshots (strongly suggested)

As we can see in the screenshots, both the look and feel and the HTML markup is the same:

Before the MR	After the MR

Does this MR meet the acceptance criteria?

Conformity

• 📋 Does this MR need a changelog?
  • I have not included a changelog entry because it's a tooling change.
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Separation of EE specific content

Related to #326345 (closed)