Update the page header in admin dashboard

[gtsiolis]

Problem to solve

Following up from #16164 (comment), the admin dashboard:

1. No longer uses an active state for the admin menu at the top.
2. Does not use a generic settings page header as the rest of the product.

Proposal

Here's a list of MVC steps that could be tackled all in one step or separate PRs.

1. Use a generic page header for all top-level pages in the admin dashboard, see screenshot below.
2. Keep the admin menu at the top active when navigating through the top-level pages in the admin dashboard.
3. Remove the sidebar menu and use the tabs for the admin dashboard #7879

Page header (BEFORE)	Page header (AFTER)

[Devansu-Yadav]

@gtsiolis I would like to work on this issue. As I do not have access to the admin dashboard, how do you suggest I could see the changes I make getting reflected on my dev environment dashboard?

[gtsiolis]

Hey @Devansu-Yadav! You can open a PR, and I'll spin up a preview environment for it—then I can help make you an admin.