Create multiple GPU node types by default

[yuvipanda]

When we setup GPUs, we currently only provision 1 node type. This means that if a community needs more RAM (but same amount of GPU), we need to provision a different node type.

Provisioning node types costs us nothing in terms of money, and makes changes like #6537 much simpler

Definition of done

• Update our docs to provision g4dn.2x and 4x for GPUs
• Update our docs to do the equivalent on GCP (after checking this doesn't increase the amount of GPUs in each node)
• Update every existing GPU cluster definition to match this