Redesign group overview UI: MVC

Overview

We accomplished ~"product discovery" for the group overview page in https://gitlab.com/gitlab-org/gitlab-ce/issues/50836.

In this issue, we'd like to accomplish the MVC for this new design and make the Overview for group pages more consistent with the alignment and design of the new project page.

Proposal

Current	Proposed

Specific changes:

• Avatar, group name, and group description now left-aligned
• Notification setting and "New project" CTA right-aligned with group avatar and name
• Leave group / request access now a link next to the 'Group' label below the group name
• Notification setting label removed in favor of icons
  • Note: we should add a "Notification setting" tooltip for clarity on mouseover
• "Sort by" label included adjacent to sorting criteria
• Search option moved inside table header next to "Sort by"