Group overview UI: Second iteration

Overview

We're continuing to iterate on the group overview page in an effort to improve the presentation of groups. In https://gitlab.com/gitlab-org/gitlab-ce/issues/54663, we explored a ~"product discovery" to realize these improvements. The proposed changes have been broken into three efforts:

1. "Barebones" styling changes to the group overview (this issue),
2. Adding pinned projects/subgroups, and
3. Adding a 7-day overview.

See https://gitlab.com/gitlab-org/gitlab-ce/issues/54663 for all other proposed changes from the discovery.

Second iteration

Changes for this iteration:

• Updated the subgroups/project lists with the latest designs (see gitlab-org/gitlab-ce#52365)
• Rename "Subgroups and projects" tab to "All"
• Move visibility icon in-line with project/group name
• Addition of middle column

Note: the containers above the first row of the table are pinned projects/subgroups and are out of scope for this iteration.