Add security dashboard keyboard shortcut

What does this MR do?

This adds two keyboard shortcuts to access security dashboard

1. Shift + u - Go to the instance security dashboard
2. g u - Go the the project security dashboard

Motivation

This was done out of curiosity as I keep moving back and forth to the security dashboards.

The most appropriate available shortcut key is u and here is why

• Preferably the letter should be part of the word SECURITY
• It should be a commonly available in both Project & Global shortcuts section

Note

Security Dashboard is an ee feature and is available in ultimate / gold plan. I hope it's okay to add shortcuts related to it, and if not how about adding a feature flag check?

Screenshots