Work with arm64 architecture

[IlanCosman]

When I try to use an arm64 architecture instance, I get the following error:

ValueError: {
  "message": "The architecture 'arm64' of the specified instance type does not match the architecture 'x86_64' of the specified AMI. Specify an instance type and an AMI that have matching architectures, and try again. You can use 'describe-instance-types' or 'describe-images' to discover the architecture of the instance type or AMI. (InvalidParameterValue)",
  "errors": {}
}

Would love for this to work! The cheapest / best performance instance is not uncommonly an arm64 one.

[ritchie46]

Ah, we can add that. Needs a few changes. I think we will land this in a couple of weeks.