Enable visibility filter on Epics menu pill count

What does this MR do and why?

:skip_visibility_check, when true, will not account for the user's access level when attempting to calculate a number for display in the sidebar (the "pill count"). This number is strong_memoize'd and cached, so this change should have negligible performance impact.

Related to #228646 (closed)

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Related to #228646 (closed)