Create an Analytics area in the navigation sidebar for groups

What does this MR do?

Add Analytics sidebar to groups navbar and move Analytics specific menu items under Analytics. The change is behind a feature flag (analytics_pages_under_group_analytics_sidebar).

Previous MR for project: !23312 (merged)

Screenshots

Does this MR meet the acceptance criteria?

Conformity

• [-] Changelog entry
• [-] Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• [-] Database guides
• Separation of EE specific content

Part of #195979 (closed)