Schedule requirements processing conditionally

In most cases projects do not have any requirements, so we can avoid
scheduling processing of any requirements which can be present in
build's artifacts.

Changelog: performance
EE: true

ee/app/workers/ee/build_finished_worker.rb

@@ -8,7 +8,9 @@ module EE
       # and `Namespace#namespace_statistics` will return stale data.
       ::Ci::Minutes::EmailNotificationService.new(build.project.reset).execute if ::Gitlab.com?
 
-      RequirementsManagement::ProcessRequirementsReportsWorker.perform_async(build.id)
+      unless build.project.requirements.empty?
+        RequirementsManagement::ProcessRequirementsReportsWorker.perform_async(build.id)
+      end
 
       super
     end

ee/spec/workers/build_finished_worker_spec.rb

@@ -57,7 +57,15 @@ RSpec.describe BuildFinishedWorker do
       end
     end
 
-    it 'processes requirements reports' do
+    it 'does not schedule processing of requirement reports by default' do
+      expect(RequirementsManagement::ProcessRequirementsReportsWorker).not_to receive(:perform_async)
+
+      subject
+    end
+
+    it 'schedules processing of requirement reports if project has requirements' do
+      create(:requirement, project: project)
+
       expect(RequirementsManagement::ProcessRequirementsReportsWorker).to receive(:perform_async)
 
       subject