Once T361174: Write to agent_id columns in the CheckUserInsert service when migration configuration allows it and T361172: Purge rows from cu_useragent are completed, WMF wikis should progressively start writing to the cu_useragent table as well as the agent_id columns in the result tables.
Acceptance criteria
- WMF wikis should have the schema migration config created in T361173 set to SCHEMA_COMPAT_OLD | SCHEMA_COMPAT_WRITE_NEW