feat(experiments): experiment_run_clickhouse.py — baseline runner

[milindsrivastava1997]

There is no experiment runner for ClickHouse baseline experiments. The existing experiment_run_e2e.py is tightly coupled to the Prometheus/PromQL pipeline. Running a ClickHouse baseline (start ClickHouse, load data, run SQL queries, collect results) requires the ad-hoc benchmark/ scripts with no experiment-runner orchestration.