Removed "Lists" entry from Requirements nav item [RUN ALL RSPEC] [RUN AS-IF-FOSS]

What does this MR do?

1. Introduces the project_sidebar_refactor feature flag for the works to be performed in the Create:Editor -- 13.11 - 14.0 -- Update Left Sidebar epic. References #326108 (closed)
2. Hides the "Lists" subitem from the "Requirements" navigation item in the left-side panel when the flag is on. References #323178 (closed).

Screenshots (strongly suggested)

	Without the flag	With the flag
Hovering
Clicking the "Requirements"

Does this MR meet the acceptance criteria?

Conformity

• 📋 Does this MR need a changelog?
  • I have included a changelog entry.
  • I have not included a changelog entry because _____.
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers
• Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Related to #323178 (closed)