Implement Help menu in super sidebar navigation

Proposal

Using <GlDisclosure>, implement the help menu in the super sidebar navigation. Clicking the ? triggers the disclosure, clicking outside closes it. All the links and functionality that exist in the current help menu should be replicated here.

Things to note

• This will be behind both the super_sidebar_nav feature flag and the navbar toggle.

Designs

See attached design files and the Navigation redesign file in figma.

Please ensure the MR is reviewed by UX