XS Add desired sharding key YAML config with backfill from ci_pipelines.project_id (5 tables)

What we need to do

These tables all have pipeline_id, so we can add project_id and use ci_pipelines.project_id to backfill

• ci_pipeline_chat_data
• ci_pipeline_messages
• ci_pipeline_variables
• p_ci_pipeline_variables
• ci_pipelines_config
• ci_trigger_requests (technically commit_id but it references the ci_pipelines table all the same) (see #502773 (closed) instead)

How to do it

Once the designation is set in the db/docs/*.yml config file, ✨ automation ✨ will handle the rest.