Move epics to premium

What does this MR do?

This is the final iteration for moving epics feature to premium edition (subepics stay in ultimate).

!24170 (merged) needs to be merged before this one.

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

Closes #37081 (closed)