Add feature flag for stopping CH data ingestion
What does this MR do and why?
This MR adds the suspend_click_house_data_ingestion worker feature flag for suspending ClickHouse data ingestion globally. The feature flag will be used for migrating ClickHouse data to a new database. During this period no INSERTs can happen. See the related issues:
- OKR: https://gitlab.com/gitlab-com/gitlab-OKRs/-/work_items/6669
- Change request: gitlab-com/gl-infra/production#17823 (closed)
MR acceptance checklist
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