[Frontend] Improve free trial page

This MR will update the free trial page structure which will improve the user experience as first touch point for our users with GitLab.

**Assets:**
https://gitlab.com/gitlab-org/gitlab-design/tree/master/progress/tim/fulfillment/svg

**Design Specs:**
https://gitlab-org.gitlab.io/gitlab-design/hosted/tim/ee%2313233-an-improved-free-trial-sign-up-experience-for-GitLab.com-spec-previews/

Before	After	After (self-managed page)

Part of gitlab-org/gitlab-ee#13233