Use linear version of User#ci_owned_runners

In this commit we're adding a feature flag
to test the linear version of the
User#ci_owned_runners method.

Changelog: performance

app/models/user.rb

@@ -1614,8 +1614,14 @@ class User < ApplicationRecord
         .joins(:runner)
         .select('ci_runners.*')
 
+      base_and_descendants = if Feature.enabled?(:linear_user_ci_owned_runners, self, default_enabled: :yaml)
+                               owned_groups.self_and_descendant_ids
+                             else
+                               Gitlab::ObjectHierarchy.new(owned_groups).base_and_descendants.select(:id)
+                             end
+
       group_runners = Ci::RunnerNamespace
-        .where(namespace_id: Gitlab::ObjectHierarchy.new(owned_groups).base_and_descendants.select(:id))
+        .where(namespace_id: base_and_descendants)
         .joins(:runner)
         .select('ci_runners.*')
 

config/feature_flags/development/linear_user_ci_owned_runners.yml

+---
+name: linear_user_ci_owned_runners
+introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/68848
+rollout_issue_url: https://gitlab.com/gitlab-org/gitlab/-/issues/339435
+milestone: '14.6'
+type: development
+group: group::access
+default_enabled: false

spec/models/user_spec.rb

@@ -3673,6 +3673,7 @@ RSpec.describe User do
   end
 
   describe '#ci_owned_runners' do
+    shared_examples 'ci_owned_runners examples' do
       let(:user) { create(:user) }
 
       shared_examples :nested_groups_owner do
@@ -3979,6 +3980,17 @@ RSpec.describe User do
       end
     end
 
+    it_behaves_like 'ci_owned_runners examples'
+
+    context 'when feature flag :linear_user_ci_owned_runners is disabled' do
+      before do
+        stub_feature_flags(linear_user_ci_owned_runners: false)
+      end
+
+      it_behaves_like 'ci_owned_runners examples'
+    end
+  end
+
   describe '#projects_with_reporter_access_limited_to' do
     let(:project1) { create(:project) }
     let(:project2) { create(:project) }