Show dependency-list-link in project sidebar based on permissions

What does this MR do?

A user, having the right permissions, should see a link to the dependency-list in a project's sidebar navigation.

A previous change moved that link under a new top-level navigation item, which is only rendered if the user has access to the security-dashboard. This prevents some users from seeing the link to the dependency-list, even if they have the right permissions.

This MR adds extra logic to correct the behaviour.

Context (Issues, Discussions and related MRs)

• https://gitlab.com/gitlab-org/gitlab-ee/issues/12250#note_200456857
• https://gitlab.com/gitlab-org/gitlab-ee/issues/12250#note_200800004
• MR for corresponding backend changes https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/15044/diffs

Before

• A user, with the permissions to read the dependency-list but not the security-dashboard, would not see a link in the navigation.

After

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

Performance 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

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team