Redesign application settings to match project settings (part 1)

What does this MR do?

Redesign application settings to match project settings by using collapsed sections:

• Visibility and access controls
• Account and limit settings
• Sign-up restrictions
• Sign-in restrictions
• Help page
• Pages

I reused existing sections to keep a scope of this MR strictly on visual change without structural one.

Are there points in the code the reviewer needs to double check?

no

Why was this MR needed?

• so application settings UI matches project settings UI
• to make application settings UI more usable by splitting it into sections

Screenshots (if relevant)

Before	After

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• API support added
• Tests added for this feature/bug
• Review
  • Has been reviewed by UX
  • Has been reviewed by Frontend
  • Has been reviewed by Backend
  • Has been reviewed by Database
• Conform by the merge request performance guides
• Conform by the style guides
• Squashed related commits together
• Internationalization required/considered
• End-to-end tests pass (package-and-qa manual pipeline job)

What are the relevant issue numbers?

https://gitlab.com/gitlab-org/gitlab-ce/issues/36274