Clickhouse model and finder for ci_finished_builds

What does this MR do and why?

• As a first iteration of the API, committing clickhouse model for ci_finished_builds clickhouse table
• The finder has methods to construct the queries we need in the API and executes the query to get the results
• Constructed the query methods by keeping the design (data we need in the UI) in mind

Design:

References

Add jobAnalytics GraphQL API to fetch data on o... (#541703 - closed)

Screenshots or screen recordings

How to set up and validate locally

Usage:

query = ClickHouse::Finders::Ci::FinishedBuildsFinder.new.select([:stage_id, :name]).mean_duration_in_seconds.p95_duration_in_seconds.rate_of_status.order_by(:mean_duration_in_seconds)

results = query.execute

puts results # might print huge data; instead, use `results.size` to verify

query.to_sql

=> "SELECT `ci_finished_builds`.`stage_id`, `ci_finished_builds`.`name`, avg(`ci_finished_builds`.`duration`) / 1000.0 AS mean_duration_in_seconds, quantile(0.95)(`ci_finished_builds`.`duration`) / 1000.0 AS p95_duration_in_seconds, countIf(`ci_finished_builds`.`status` = 'success') / count() * 100 AS rate_of_success FROM `ci_finished_builds` GROUP BY stage_id, name ORDER BY mean_duration_in_seconds ASC"

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