Add message in Danger for ClickHouse review

What does this MR do and why?

Add ClickHouse category to merge requests.

When files are added or changed in db/clickhouse or really anything with click_house or clickhouse in the filepath, we should ask for review from the clickhouse team.

Manages labels for clickhouse and clickhousereview pending and clickhouseapproved (no "reviewed" category) to support review flow, a bit similar to database.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to gitlab-org/ruby/gems/gitlab-dangerfiles#71 (closed)