Add the AvailabilityZone column in the Azure catalog

[WoosukKwon]

Another question: do all zones in the same region always offer the same set of VM types? If not, why don't we add the AvailabilityZone column here?

Previously , we didn't find any price difference between AZs for Azure, so no AZ name was added. However, seems there is data transfer cost between zones ($0.01 /GB). We may want to investigate adding AZ to the catalog and our code for Azure.

Originally posted by @Michaelvll in #4 (comment)