Add top_nav_menu_sections component

• Requirements (issue)
• Tasks (epic)
• Full Context Spike MR (permanent draft)
• All MR Parts...
  • Add top_nav_menu_sections component

What does this MR do?

This MR adds a top_nav_menu_sections component which helps simplify a lot in the top nav redesign.

Screenshots (strongly suggested)

How to test?

You will need to enable the :combined_menu feature flag. Then, there should be no changes to the top nav menu, since this MR should be a pure refactor.

Before	After

Does this MR meet the acceptance criteria?

Conformity

• [ ] I have included a changelog entry, or it's not needed. (Does this MR need a changelog?) Not needed since no user-facing change.
• I have added/updated documentation, or it's not needed. (Is documentation required?)
• I have properly separated EE content from FOSS, or this MR is FOSS only. (Where should EE code go?)
• I have added information for database reviewers in the MR description, or it's not needed. (Does this MR have database related changes?)
• I have self-reviewed this MR per code review guidelines.
• This MR does not harm performance, or I have asked a reviewer to help assess the performance impact. (Merge request performance guidelines)
• I have followed the style guides.

Related to #301143 (closed)