Fix broken ClickHouse projections on ci_finished_builds

What does this MR do and why?

Fixes a broken state on ci_finished_builds in ClickHouse, where all mutations (including DROP PROJECTION) fail with:

Missing columns: 'artifacts_size' 'when' 'retries_count' 'failure_reason' ...

• The by_project_pipeline_finished_at_name projection used SELECT * and was materialized before 11 new columns were added, leaving its on-disk parts with missing columns.
• This blocked all mutations on the table due to deduplicate_merge_projection_mode = 'rebuild'.
• Recreate the projection as by_project_pipeline_finished_at_name_v2 with explicit columns, no-op the blocked migration, and re-add the build_stats projection in a new migration.

What this MR does

1. No-ops 20260224114553 — This migration was stuck on staging/production because it runs mutations on the broken table. It is replaced by a later migration.
2. New migration 20260302052651 — Drops the broken by_project_pipeline_finished_at_name projection and recreates it as by_project_pipeline_finished_at_name_v2 with explicit columns instead of SELECT *. Using a new name avoids race conditions between the async DROP and the ADD.
3. New migration 20260302052652 — Re-does what the no-op'd migration originally did: adds build_stats_by_project_pipeline_finished_at_name_stage_name, materializes it, and drops the old build_stats_by_project_pipeline_name_stage_name.
4. Updates db/click_house/main.sql — Replaces SELECT * with explicit column list in the projection definition.

Pre-deployment step for staging/production

• Before deploying, stuck mutations must be killed manually:

KILL MUTATION WHERE table = 'ci_finished_builds' AND is_done = 0;

References

#591727 (closed)

How to set up and validate locally

1. Run ClickHouse migrations:

 bundle exec rake gitlab:clickhouse:migrate

2. Connect to the local ClickHouse console and verify projections:

SELECT name, type FROM system.projection_parts
   WHERE table = 'ci_finished_builds'
   GROUP BY name, type;

3. Verify by_project_pipeline_finished_at_name no longer exists and by_project_pipeline_finished_at_name_v2 is present:

SHOW CREATE TABLE ci_finished_builds;

4. Verify mutations are not stuck:

SELECT * FROM system.mutations WHERE table = 'ci_finished_builds' AND is_done = 0;

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