Add new module to get available upgrade versions for an AKS cluster

[ewsct]

SUMMARY

Get the upgrade versions available for a managed Azure Container Service (AKS) instance.
Essentially it has similar information in its output as command az aks get-upgrades.

Fixes #377

ISSUE TYPE

• New Module Pull Request

COMPONENT NAME

• module: azure_rm_aksupgrade_info

ADDITIONAL INFORMATION

When you upgrade an AKS cluster, Kubernetes minor versions cannot be skipped. For example, upgrades between 1.12.x -> 1.13.x or 1.13.x -> 1.14.x are allowed, however 1.12.x -> 1.14.x is not. So you can not simply take the latest available version for new AKS instance. And that is why we need az aks get-upgrades command, which gets cluster name and its resource group as parameters.
This is a separate module (and not part of an existing one) because it is separate both in Azure SDK and az cli tool. So it would be wise to follow the same approach here, taking into account it generates the same information in its output.

Example:

"available_upgrades": {
        "agent_pool_profiles": [
            {
                "kubernetes_version": "1.18.1",
                "name": null,
                "os_type": "Linux",
                "upgrades": [
                    {
                        "is_preview": null,
                        "kubernetes_version": "1.19.3"
                    }
                ]
            }
        ],
        "control_plane_profile": {
            "kubernetes_version": "1.18.1",
            "name": null,
            "os_type": "Linux",
            "upgrades": [
                {
                    "is_preview": null,
                    "kubernetes_version": "1.19.3"
                }
            ]
        }
    },

[Fred-sun]

@ewscat Please add these two lines to file tests/sanity/ignore-2.10.txt. Thank you very much!

[ewsct]

@ewscat Please add these two lines to file tests/sanity/ignore-2.10.txt. Thank you very much!

@Fred-sun it's done 😎

[Fred-sun]

@ewscat Please add these two lines to file tests/sanity/ignore-2.10.txt. Thank you very much!

@Fred-sun it's done 😎

@ewscat Thanks for your update! I will push for merged!