Add view tests for project sidebar - security & compliance

What does this MR do?

This MR adds tests to verify that the template partials, responsible for rendering the 'Security & Compliance' navigation, are displaying the correct nav-items based on the current user's permissions:

• Read access to both the dependency list and the security dashboard
• Only read access to either
• No access at all

Note: this is a follow up to this discussion: https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/15066#note_202074834

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation created/updated or follow-up review issue created
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content