Validate qualified node AMI exists in snow devices

There is an AMI lookup logic in CAPAS where if the amiID is empty in machine, it looks at the device and find a qualified, suitable node AMI in the device based on the specified K8s version and OS family, to create the node machine.

We need to copy parts of the AMI lookup logic to EKS-A preflight validation, to fail ahead if no valid AMI exists in the devices.

Start by locating the existing CAPAS AMI lookup logic and the EKS-A preflight validation entry point. Compare how a machine with an empty amiID selects a qualified node AMI from a Snow device using the Kubernetes version and OS family. Done means preflight fails when no valid AMI exists in the devices, before node-machine creation.

Written by the indexing model from the issue text.