XS Add sharding key YAML config to ci_pipelines & p_ci_pipelines

What we need to do

The ci_pipelines table has a project_id key, but didn't get the designation automatically a few months ago when the Cells team sent out all the initial MRs.

I'm not sure if there's something blocking this having to do with partitioning.

How to do it

1. Find out if there's any reason we can't add the sharding key designation immediately and have all the automation work.
2. Open up https://gitlab.com/gitlab-org/gitlab/-/blob/master/db/docs/ci_pipelines.yml

  table_name: ci_pipelines
  classes:
  - Ci::Pipeline
  feature_categories:
  - continuous_integration
  description: TODO
  introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/commit/c6ae290cea4b88ecaa9cfe0bc9d88e8fd32070c1
  milestone: '9.0'
  gitlab_schema: gitlab_ci
+ sharding_key:
+   project_id: projects