Add tooltip to requirement controls

What does this MR do and why?

Add a description tooltip for each control in the dropdown so that users know the benefit of using that control without having to open the docs.

References

Related to #536327 (closed)

Screenshots or screen recordings

How to set up and validate locally

1. Navigate to a Group > Secure > Compliance Center
2. Click New Framework
3. Click Create blank Framework
4. Click New requirement to open modal
5. Open dropdown by clicking Choose a GitLab control
6. Hover over control items to verify that a tooltip is rendered

MR acceptance checklist

Evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.