Add new "Overview" tab on user profile page

Problem to solve

We have a lot of ambitious ideas related to the user profile page. In a first step we explored a redesign of the current page UI via https://gitlab.com/gitlab-org/gitlab-ce/issues/24243 ~"product discovery" that allows us to build on top of it. Functionality-wise, "pinned projects" are an enhancement we want to bring in very soon to allow users to highlight specific projects they have created/contributed to.

To achieve this, there are related design changes required that we should get in via this issue.

Proposal

• Add new "Overview" tab to user profile page
• Implement two column layout
• Create 6 months contribution graph variant
• Create initial activity feed variant that shows first 5 entries max on high viewports, with "View all…" link (redesigned UI is out of scope and covered via https://gitlab.com/gitlab-org/gitlab-ce/issues/48321)
• Create initial project list that shows first 10 entries max on high viewports, with "View all…" link (details regarding which projects to display to define)

Vision	No technology	No activity	No activity, no projects	MVC

What does success look like, and how can we measure that?

(If no way to measure success, link to an issue that will implement a way to measure this)