consolidate incident management documentation

We have several issues with our incident management documentation:

• we have documentation in several places with different/outdated content:
  • https://about.gitlab.com/handbook/engineering/infrastructure/incident-management/
  • https://gitlab.com/gitlab-com/runbooks/blob/master/howto/manage-production-incidents.md
  • https://gitlab.com/gitlab-com/runbooks/blob/master/incidents/general_incidents.md
  • https://gitlab.com/gitlab-com/runbooks/blob/master/incidents/database.md
• The handbook page is a very long read which is fine to learn all about the processes if you have time but does not work if you have an incident and need to figure what to do ASAP.
• We have no documentation on
  • how to find the EOC/IMOC/CMOC
  • how to page the EOC/IMOC/CMOC
  • chatbots and their usage

We need to consolidate this documentation and make it easy to find and useful for everybody during an incident.