collab: Fix writing LLM rate limit events to Clickhouse (#16367)

This PR fixes the writing of LLM rate limit events to Clickhouse.

We had a table in the table name: `llm_rate_limits` instead of
`llm_rate_limit_events`.

I also extracted a helper function to write to Clickhouse so we can use
it anywhere we need to.

Release Notes:

- N/A