Shared groups fix for group/:id/members/all REST/GraphQL APIs

What does this MR do?

groups/:id/members/all would not return users of groups invited to the current group.
Added relation to seek for users from :shared_from_groups within the current group, similar to how projects do it in project_invited_groups of member_finder.rb.
Fixes: #321694 (closed)
Fixes: POV45

Conformity

• [Y] I have included changelog trailers, or none are needed. (Does this MR need a changelog?)
• [Y] This MR does not harm performance, or I have asked a reviewer to help assess the performance impact. (Merge request performance guidelines)
• [Y] I have followed the style guides.

Availability and Testing

• [Y] I have added/updated tests following the Testing Guide, or it's not needed. (Consider all test levels. See the Test Planning Process.)