Validate FKs p_ci_stages self managed

Ref: #439065 (closed)

What does this MR do and why?

Following up !145899 (merged) where we successfully added this FK to p_ci_stages for gitlab.com.

This MR validates our new FK for self-managed and add the FK between the routing table.

Why are we doing this?

This is a prerequisite in order to partition this table.

https://docs.gitlab.com/ee/development/database/partitioning/list.html#step-7---re-point-foreign-keys-to-parent-table