Use Group linear ancestor scopes

In this commit we're replacing the recursive ancestors scope in
the `Group` model, for their linear version.

Changelog: performance
EE: true

config/feature_flags/development/linear_ee_group_ancestor_scopes.yml

+---
+name: linear_ee_group_ancestor_scopes
+introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/70708
+rollout_issue_url: https://gitlab.com/gitlab-org/gitlab/-/issues/341350
+milestone: '14.4'
+type: development
+group: group::access
+default_enabled: false

ee/app/models/ee/group.rb

@@ -614,7 +614,13 @@ module EE
     end
 
     def invited_or_shared_group_members(groups)
-      ::GroupMember.active_without_invites_and_requests.where(source_id: ::Gitlab::ObjectHierarchy.new(groups).base_and_ancestors)
+      groups_and_ancestors = if ::Feature.enabled?(:linear_ee_group_ancestor_scopes, self, default_enabled: :yaml)
+                               groups.self_and_ancestors
+                             else
+                               ::Gitlab::ObjectHierarchy.new(groups).base_and_ancestors
+                             end
+
+      ::GroupMember.active_without_invites_and_requests.where(source_id: groups_and_ancestors)
     end
 
     override :_safe_read_repository_read_only_column