Adds mergeRequestInteraction to GraphQL user type

What does this MR do and why?

Adds mergeRequestInteraction GraphQL type to the MemberInterface GraphQL object. This type accepts a merge request IID which will be used to find the merge request.

query {
  project(fullPath:"gitlab-org/gitlab-test") {
    projectMembers {
      nodes {
         mergeRequestInteraction(id:"gid://gitlab/MergeRequest/96") {
          canMerge
        }
      }
    }
  }
}

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Closes #329783 (closed)