Product Discovery to inform users about Security Dashboard in lower tiers

Problem to solve

Security Dashboard is available for GitLab Ultimate only. This makes users without this license unaware of its existence.

We should promote the feature in lower tiers, so people can consider to upgrade.

Further details

We don't do promotion in gitlab-ce codebase. This issue should be implemented entirely in gitlab-ee for the following cases:

1. GitLab Premium
2. GitLab Starter
3. GitLab EE without a license

Proposal

Show some promotion for the Security Dashboard. We can always show the menu entry, and use an info message if users click on it.

What does success look like, and how can we measure that?

Users upgrade to GitLab Ultimate.