[Feature] OSDiskSizeGB set to max available by default in NAP

[wdarko1]

Desired Behavior: For NAP managed nodes, AKS by default provisions an Ephemeral OS disk with a size that scales according to the total temp storage of the VM SKU so long as the temp is at least 128GiB, even if no size was specified. (see [OSDiskSizeGB documentation] (https://learn.microsoft.com/azure/aks/concepts-storage#ephemeral-os-disks) for more details)

ETA: backlog

Current behavior: Right now NAP uses partial ephemeral storage, not necessarily the full available storage by default. NAP can set the OS disk size to exactly the requested OSDiskSizeGB in the [AKSNodeClass] (https://learn.microsoft.com/azure/aks/node-auto-provisioning-aksnodeclass) custom resource definition, but will not default to the max unless specified. If not specified in the AKSNodeClass, the default is 128GB