Improve source column in membership table

Follow up to #429341 (closed). In addition to the filter, I'd also like to see us improve the Source column in the table to account for the Inherited shared case by indicating that the source includes both an originating group and that is has been inherited.

Current state

Proposal

Simplify the display to show the "most relevant" part of the membership path. If it is direct, just show direct. If it is inherited or shared we just show inherited or shared. If it is both we would show just the last step.

Add text indicating the type of source as follows:

Direct member

Member of a group/project that inherits from a group higher up the tree

Member of a group/project that is from a group that is shared with this group/project

Implementation guide

Frontend

1. In app/assets/javascripts/members/components/table/member_source.vue check isSharedMember attribute from backend and update UI accordingly

Backend

!150545 (merged) should be a good starting point.