Create background migration to copy builds_metadata records to new tables

What does this MR do and why?

Create background migration to backfill job definitions, p_ci_builds, job artifacts, environments, etc

Changelog: other

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Before	After

How to set up and validate locally

MR acceptance checklist

Evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

Related to #552069