Modify our handbook/change request template for error checking

One of the corrective actions for https://gitlab.com/gitlab-com/gl-infra/infrastructure/issues/6027 is to better the way we perform work by understanding and looking out for potential failure scenarios and alerting on these. Utilize this issue to track modifications to be done to our handbook, as well as the change request issue template to include the language necessary for us to better understand and watch for failure scenarios during scheduled maintenance work.