CML being able to launch AWS Spot instances

[AndreGodinho7]

The AWS EC2 spot instances seem to be cheaper than on-demand EC2 instances. It would be great to be able to train models in spot instances with CML according to a set of possible instances (e.g., g4dn.xlarge, g4dn.2xlarge, etc.), while defining a maximum maintain target cost for the spot instance. After training, the instance would be then terminated.