Adjust terminology around machine types in the Reference Architectures to be example based to increase awareness

For each Reference Architecture size we list out machine types for the 3 main providers (AWS, GCP, Azure). We also call out on the main page that newer machine types with newer CPUs (or indeed different types like ARM) can be used instead.

This is a supported and indeed intended designed choice of the Reference Architectures - We do not require customers to use the exact machine types for numerous good reasons and ultimately stress as long as they are meeting the base requirements and not knowingly using an older or weaker CPU that the lowest common denominator ones we specifically test against then it is supported to switch up.

To reflect this further we'll explore adjusting the terminology to increase awareness. Specifically we'll adjust each Ref Arch table to highlight the machine type listed is an example. We already do this for the Cloud Native Hybrid node pools so this is to expand that for better awareness and surfacing. It will also allow us to explore bringing in ARM machine types where applicable as an additional example.