(aws): Ability to specify a subnet

[shanman190]

Is your feature request related to a problem?
For anything other than the default VPC, you need to specify the subnet that the instance should be launched in as part of the RunInstances API call. At the moment, the vpc id is available to be set, but the subnet is not.

Which solution do you suggest?
Expose an optional subnet field that propagates all the way into the RunInstances API call.

Which alternative solutions exist?
None

Additional context

[89luca89]

Thanks @shanman190 for the feedback!
I'll work on this 👍