Add data consistency for PipelineNotificationWorker

What does this MR do?

Utilize new Sidekiq read-only database replicas capabilities (introduced in !55881 (merged)) for PipelineNotificationWorker.

Data consistency is set to :sticky, which will allow the job to use a replica as long as possible. It switches to primary either on write or on long replication lag.

Feature flag: load_balancing_for_pipeline_notification_worker (disabled by default)
Rollout issue: #336517 (closed)

Does this MR meet the acceptance criteria?

Conformity

• I have included changelog trailers, or none are needed. (Does this MR need a changelog?)
• [-] I have added/updated documentation, or it's not needed. (Is documentation required?)
• [-] I have properly separated EE content from FOSS, or this MR is FOSS only. (Where should EE code go?)
• I have added information for database reviewers in the MR description, or it's not needed. (Does this MR have database related changes?)
• I have self-reviewed this MR per code review guidelines.
• This MR does not harm performance, or I have asked a reviewer to help assess the performance impact. (Merge request performance guidelines)
• I have followed the style guides.
• This change is backwards compatible across updates, or this does not apply.

#324374 (closed)