Create second partition for ci_builds_metadata

Description

As part of the work required for CI Time decay we want create a second partition for ci_builds_metadata to make sure our new architecture behaves as expected.

Technical Proposal

• Write a migration to create a second partition for ci_builds_metadata

• https://www.postgresql.org/docs/current/ddl-partitioning.html#DDL-PARTITIONING-INHERITANCE-MAINTENANCE