Implementation for Set-AzureVMChefExtension cmdlet

Changes for SetAzureVMChefExtension cmdlet.

Chef RFC ref: https://github.com/muktaa/chef-rfc/blob/muktaa/rfc-chef-extn-azure-cmdlet/rfc0001-chef-extn-azure-cmdlet.md

Lean kit Card ref: https://chef.leankit.com/Boards/View/101745940/102190746

@muktaa @kaustubh-d