Add tracking ci jobs to the post-deploy pipeline

What does this MR do and why?

Updates the PostDeployMigrations::Deployment class to follow the same logic the Deployments::DeploymentTracker follows:

• Tracks by default on security, this is because auto-deploy branches only exist on Security
• Fetches an intersect between the security auto-deploy branch and the canonical default branch, if found tracks also on canonical.
• Track a product deployment to keep the metadata updated.

To avoid duplication between both trackers (deployments and post-migrations) it introduces an interface that defines methods for both classes.

Related to gitlab-com/gl-infra/delivery#2363 (closed)

Author Check-list

• [-] Has documentation been updated?