Cells: Iteration 2: Fix all cross-joins related to `User can create group`

Problem

As a result https://gitlab.com/gitlab-org/gitlab/-/issues/40984+ we will create a number of issues.

From that list we need to pick cross-joins that were identified by Cells: Iteration 2: Record all queries performe... (#404762 - closed).

This issue serves as a placeholder to indicate that we need to choose which issues we need to work on, and should be closed once as those are identified.

Possible list:

app/finders/merge_requests_finder.rb:    items = items.allow_cross_joins_across_databases(url: "https://gitlab.com/gitlab-org/gitlab/-/issues/417462")
app/models/group.rb:      .allow_cross_joins_across_databases(url: "https://gitlab.com/gitlab-org/gitlab/-/issues/417455")
app/models/group.rb:                    ]).allow_cross_joins_across_databases(url: "https://gitlab.com/gitlab-org/gitlab/-/issues/417455") # failed in spec/tasks/gitlab/user_management_rake_spec.rb
app/models/group.rb:      .allow_cross_joins_across_databases(url: "https://gitlab.com/gitlab-org/gitlab/-/issues/417455")
app/models/group.rb:    ::Gitlab::Database.allow_cross_joins_across_databases(url: "https://gitlab.com/gitlab-org/gitlab/-/issues/417455") do
app/models/member.rb:    .allow_cross_joins_across_databases(url: "https://gitlab.com/gitlab-org/gitlab/-/issues/417456")
app/models/member.rb:      .allow_cross_joins_across_databases(url: "https://gitlab.com/gitlab-org/gitlab/-/issues/417456")
app/models/member.rb:                .allow_cross_joins_across_databases(url: "https://gitlab.com/gitlab-org/gitlab/-/issues/417456")
app/models/member.rb:        .allow_cross_joins_across_databases(url: "https://gitlab.com/gitlab-org/gitlab/-/issues/417456")
lib/api/helpers/members_helpers.rb:        members = members.allow_cross_joins_across_databases(url: "https://gitlab.com/gitlab-org/gitlab/-/issues/417456")