CI: add use Azure
numba project added support for Azure CI pipelines: https://github.com/numba/numba/pull/3303

https://azure.microsoft.com/en-us/services/devops/pipelines/

looks like 10 parallel pipelines for open-source projects on mac, linux, windows OS.

we could replace appveyor with this I think.

cc @pandas-dev/pandas-core 