Include a Lab table and references from builds and checkouts

Lab identity is stored inside JSON today:

• Builds: misc.lab
• Tests: misc.runtime (KCIDB naming)

Ingester

• On ingest, populate lab when the submission provides it (misc.lab for builds, misc.runtime for tests).
• Reuse existing standardize_labs() behavior (automatic lab names → automatic_lab, fallback to origin when missing).
• Write the resolved value to the column, not only the raw JSON field.

Acceptance criteria
• New ingestion populates lab on builds and tests when data is available.
• Hot-path queries use the column, not JSON extraction, for lab filtering/grouping.

Start in the ingester and trace how build misc.lab and test misc.runtime are read, then locate standardize_labs() and the lab column. Verify that ingestion stores the resolved lab value for both submission types and that lab filtering and grouping use the column rather than JSON extraction.

Written by the indexing model from the issue text.