Record timestamp of status updates for container repositories

What does this MR do and why?

• Add a column status_updated_at to ContainerRepository model to record the timestamp of the status updates #378384 (closed).
• Write test cases for the same when ContainerRepository is deleted for both delete_scheduled and delete_ongoing.

Screenshots or screen recordings

N/A

How to set up and validate locally

• Setup GDK as done normally
• Run bin/rspec ./spec/models/container_repository_spec.rb

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.