Feature Request: Post-processor to upload VHD to Azure

[ghost]

This issue was originally opened by @ptveite as hashicorp/packer#5477. It was migrated here as a result of the Packer plugin split. The original body of the issue is below.

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I'm using the Hyper-V iso builder to make a base image for use with Azure BYOL, and would like to have a post-processor that will convert my vhdx output to vhd and upload it to an Azure storage container.