Include subgroup membership groups in the forks list

What does this MR do and why?

Allows the subgroup membership groups to be visible in the project URL namespace list on the fork project page.

A group that someone is added to by way of membership in subgroup that’s added to that group can not be forked into by members of the subgroup. The target group did not appear in the list of Groups and subgroups that can be forked into. This MR fixes this issue by including the missing authorized groups with shared membership in that list.

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Related to #331529 (closed)