fix(admin): Add admin navigation and access gate

[cmp5987]

What type of PR is this?

/kind bug
/kind cleanup

What this PR does / why we need it:

There was an issue with the rebase for Admin view that lead to the Admin navigation items getting removed.

• This PR adds the 'admin' view to the navigation
• Moves logic for 'checking' loading/error state to the AccessGate
• Moves logic for 'checking' admin status to a newly created 'AdminAccessGate'
• Adds a 'sm' size styling for Buttons and hover states for 'outline' buttons
• Moves 'PageWrapper' to 'features' as it now has a useHook and several components (cleanup).