Updated design of merge request homepage

What does this MR do and why?

Updated the design to be tabular format instead. Each merge request row now includes more data that is relevant to the user.

MR acceptance checklist

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

Screenshots or screen recordings

How to set up and validate locally

• Enable merge_request_dashboard feature flag
• Visit http://gdk.test:3000/dashboard/merge_requests