Add Azure support

[feiskyer]

#229 removed Azure support temporarily, we should add Azure support back.

TODOs:

• Bring azure cloud provider back Add azure cloud provider #454
• Add VMSS support
• Add Availability Set ( standard VM type) support Add support for Azure virtual machine availability sets (VMAS) #514
• Multiple node groups Support multiple node groups on Azure #542
• TemplateNodeInfo not supported
• Reduce API calls and avoid touching Azure rate limits Reduce API calls and avoid touching Azure rate limits #552
• Add AKS support
• Unit tests
• Documentations Document useInstanceMetadata settings for Azure standard vmType #641

Depends on: Support VMSS in azure cloud provider kubernetes/kubernetes#43287

[MaciekPytel]

This is already discussed at #133 and kubernetes/kubernetes#47511 and some volunteers have posted there. Since none of regular CA maintainers works on Azure, or has any knowledge of it, we fully depend on community for this.

[feiskyer]

@MaciekPytel Yep, I'd like to add this back. This will be depending on VMSS feature on Azure.

[feiskyer]

/assign

[feiskyer]

/label azure

[feiskyer]

Initial Azure support has been added in cluster-autosclaer v1.2.0. Closing this issue.

Will open another issue to track AKS support

[feiskyer]

Opened #753 for AKS support