Eliminate analytics FF helper methods

What does this MR do?

This MR eliminates, old feature flags which should have been removed long time ago.

Feature flags:

• cycle_analytics (group level VSA was introduced last year, default enabled since months)
• productivity_analytics (introduced last year, default enabled since last year)
• group_merge_request_analytics (only empty page was introduced, the feature was put on hold. For now I disabled the page)
• project_merge_request_analytics (default enabled in 13.3)

group_coverage_reports Feature Flag:

I'm not quite familiar with this feature so I kept it as is. The documentation allows the feature to be turned off so I preserved that functionality. I added a licensed FF yml entry.

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
• Informed Infrastructure department of a default or new setting change, if applicable per definition of done

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