Add WriteBuffer for Ai::UserMetrics

config/initializers/1_settings.rb

ee/app/models/ai/user_metrics.rb

ee/app/models/concerns/analytics/has_write_buffer.rb

ee/app/workers/all_queues.yml

...nalytics/dump_ai_user_metrics_write_buffer_cron_worker.rb

...rkers/concerns/analytics/write_buffer_processor_worker.rb

ee/app/workers/usage_events/dump_write_buffer_cron_worker.rb

ee/lib/ai/usage_event_write_buffer.rb

ee/lib/analytics/ai_user_metrics_database_write_buffer.rb

ee/lib/analytics/database_write_buffer.rb

...b/analytics/ai_user_metrics_database_write_buffer_spec.rb

ee/spec/lib/analytics/database_write_buffer_spec.rb

ee/spec/models/ai/user_metrics_spec.rb

...ics/dump_ai_user_metrics_write_buffer_cron_worker_spec.rb

...orkers/usage_events/dump_write_buffer_cron_worker_spec.rb

lib/click_house/write_buffer.rb

lib/gitlab/redis/backwards_compatibility.rb