Setup CI instance about infra

[escattone]

@limed I'm adding the following just so I can also use this issue within the MDN sprint.

User story

As an MDN developer, I want to ensure our CI code works within IT's CI infrastructure so that we can continue to run tests, send notifications, build and register Docker images, and deploy code.

Acceptance criteria

• Jenkins service (with admin privileges for @limed, @jwhitlock and @escattone)
• The Kuma Jenkinsfile runs successfully for the default case as well as the following custom branches:
  • master
  • stage-push
  • stage-integration-tests
• The Kumascript Jenkinsfile runs successfully for the default case as well as the following custom branches:
  • master
  • stage-push
• Notifications successfully sent to IRC #mdndev
• Docker images successfully registered on https://hub.docker.com/
• Successful deployments to new stage instance
• Follow-on tasks are documented

Tasks

• Spin-up Jenkins service (@limed)
• Configure Jenkins for multi-branch pipelines for Kuma and Kumascript (@limed, @escattone)
• Modify the Groovy utils in Kuma to handle the new multi-branch pipeline names and select the appropriate region (@escattone)
• Modify new stage set-up to use DockerHub rather than quay.io (@escattone)
• Test both the Kuma and Kumascript Jenkinsfile (as detailed in the acceptance criteria) (@escattone)

[escattone]

mdn/kumascript#767

[escattone]

• The Kuma Jenkinsfile runs successfully for the default case as well as the following custom branches: master, stage-push, and stage-integration-tests (NOTE: the stage-integration-tests branch builds with errors, but they are due to the unreliability of the tests)
• The Kumascript Jenkinsfile runs successfully for the default case as well as the following custom branches: master and stage-push
• Notifications successfully sent to IRC #mdndev
• Docker images successfully registered on https://hub.docker.com/
• Successful deployments of Kuma and Kumascript to new stage instance

[escattone]

Within this issue, I didn't include the task of creating and testing a Jenkinsfile-based multi-branch pipeline for the https://github.com/mdn/interactive-examples repo. This will be a follow-on task that we will track in a new issue.

See #41