Set AutoMergeProcessWorker data consistency to sticky

There's not a lot of immediate benefit to doing this, but we are
preparing some other changes that will move a very high-volume read
query out of the PipelineProcessWorker and into this worker, where
it will hit replicas before the merge process actually starts.

app/workers/auto_merge_process_worker.rb

@@ -3,7 +3,7 @@
 class AutoMergeProcessWorker # rubocop:disable Scalability/IdempotentWorker
   include ApplicationWorker
 
-  data_consistency :always
+  data_consistency :sticky, feature_flag: :auto_merge_process_worker_sticky
 
   sidekiq_options retry: 3
 

config/feature_flags/worker/auto_merge_process_worker_sticky.yml

+---
+name: auto_merge_process_worker_sticky
+feature_issue_url: https://gitlab.com/gitlab-org/gitlab/-/issues/483008
+introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/167234
+rollout_issue_url: https://gitlab.com/gitlab-org/gitlab/-/issues/496567
+milestone: '17.5'
+group: group::ci platform
+type: worker
+default_enabled: false