Add analytics pages to Project Analytics sidebar

What does this MR do?

Moves the analytics specific menu items from the project sidebar under the Analytics menu.

• Add unless option (lambda) to nav_link to have a flexible way to skip matching the current action.
• Move analytics specific pages to Analytics sidebar.
• Add the change behind a feature flag: analytics_pages_under_project_analytics_sidebar

Screenshots

Before	After

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

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• [-] Label as security and @ mention @gitlab-com/gl-security/appsec
• [-] The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• [-] Security reports checked/validated by a reviewer from the AppSec team

Part of #38318 (closed)