bug: not considering all AZ, restrictions on VM SKU

[alexeldeib]

/kind bug

What steps did you take and what happened:
compute.ResourceSkusClient returns the first page of a paginated results set.

There are two issues in the current implementation. Not all the pages are iterated. This results in users potentially erroring out on valid SKUs. There may also be restrictions either at the Location level for a given subscription, or at the Zone level.

If a machine SKU exists in a Location but is Location restricted, you may not deploy this SKU at all.

If a machine SKU exists in a Location but all its listed Zones are restricted (or there are none listed), you may deploy the SKU but only using Fault/Update domains.

What did you expect to happen:
Iterate the whole result result, and properly handle restrictions.