Add security configuration navigation item

What does this MR do?

It adds a new item Configuration to a project's security tap.

The item links to a security configuration page that has already been deployed to production.

Note: Since this is the last piece of #13638 (closed) it also adds documentation.

Screenshots

Navigation Flyout	Configuration page with active nav

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• 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

Related to #13638 (closed)