Include production engineers in CI runners management

Steps needed to be completed to include production engineers into CI runners management:

  • prepare/update Runner's documentation in configuration and management context - https://dev.gitlab.org/cookbooks/chef-repo/merge_requests/102
  • prepare runbooks with description of common situations:
    • high error auto-scaled machines count
    • digital ocean rate limiting
    • runner's update procedure
  • move all runner's and runner-related host configuration to chef
    • prepare/update cookbook
    • create shared-runners-manager-2.gitlab.com (#123 (closed))
    • configure runners on shared-runners-manager-2.gitlab.comand add it to GitLab.com
    • migrate shared-runners-manager-1.gitlab.com to chef
    • migrate docker-ci-1.gitlap.com to chef
    • migrate docker-ci-2.gitlap.com to chef
  • remove unused roles from chef
    • gitlab-shared-runners-manager
    • gitlab-runners-manager
  • prepare runbooks for docker registry proxy and cache server
  • add monitoring for docker registry proxy and cache server

/cc @ayufan