Dynamic cloud computing scaling

STF Task Description:

• MUST: Add dynamic-scaling of CPU resources by being able to auto-spawn new workers with cloud resources
  • Need to be able to provide different worker profiles (small / medium / large / extra-large ?).
  • Need safeguards/limits to not exceed a budget / a resource limit
  • Need logic to setup workers with appropriate build chroots / autopkgtest VM images / etc.
  • Need also logic to give back the dynamic workers when they have been idle
  • Static workers should have higher priority for assignation of work requests so that dynamic workers can be idle and shut down after a while
  • Need to support Amazon EC2 but must be easy to extend to add support for other cloud providers
  • Need to provide an overview of the workers and dynamic.