vm: migrate to use newer style of azure-mgmt-compute

[yugangw-msft]

We should do it, but just when we can get it done. I thought I could take care of it through the work of supporting zone resilient image, but appears more extensive updates involved than I have expected.
(Thanks to improved CI work, the wheel is available at Azure/azure-sdk-for-python#1930 to try out)

For anyone with cycles, please feel free to grab this item; otherwise I will come back to this next week.
//CC: @mayurid @tjprescott @derekbekoe @lmazuel