Merge branch '20909-use-total-count-instead-of-size' into 'master'

changes from using size to count and caching it to get the number of members in a group

- [x] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- [x] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)
- [x] API support added
- Tests
  - [x] Added for this feature/bug
  - [x] All builds are passing
- [x] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [x] Branch has no merge conflicts with `master` (if you do - rebase it please)
- [x] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)
Closes #20909

See merge request !5935

CHANGELOG

@@ -14,6 +14,7 @@ v 8.11.2 (unreleased)
 v 8.11.1 (unreleased)
   - Does not halt the GitHub import process when an error occurs
   - Fix file links on project page when default view is Files !5933
+  - Change using size to use count and caching it for number of group members
 
 v 8.11.0
   - Use test coverage value from the latest successful pipeline in badge. !5862

app/views/groups/group_members/index.html.haml

@@ -17,7 +17,7 @@
     .panel-heading
       %strong #{@group.name}
       group members
-      %span.badge= @members.size
+      %span.badge= @members.total_count
       .controls
         = form_tag group_group_members_path(@group), method: :get, class: 'form-inline member-search-form'  do
           .form-group