Adding duplicate FK to deployments

What does this MR do and why?

Adding duplicate FK to deployments

This adds FK to deployment id_convert_to_bigint PK column for deployments bigint migration

We add these FK so we can swap them and drop the existing one on deployments.

Changelog: changed

References

Following: https://docs.gitlab.com/development/database/foreign_keys/#adding-the-fk-constraint-not-valid

Screenshots or screen recordings

Before	After

How to set up and validate locally

Run the migrations, and validate async via https://docs.gitlab.com/development/database/foreign_keys/#adding-the-fk-constraint-not-valid

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 #581422 (closed)