Create a training issue for multi-version compatibility

As a follow-up to the upgrade strategies audit, we want to create a lightweight training issue to ensure current and new engineers are aware of multi-version compatibility example problems and strategies to identify and prevent.

Tasks

• Gather what is currently documented
• Add any additional documentation to help with upgrade strategies
• Gather what pages and videos we want every engineer to review
• Investigate whether GitLab L&D can be leveraged here
• Add to onboarding issue template this training
  • Engineering onboarding tasks: https://gitlab.com/gitlab-com/people-group/people-operations/employment-templates/-/blob/master/.gitlab/issue_templates/onboarding_tasks/department_development.md

Google doc to collect resources and identify gaps