[Az.Functions]: Need to support switching between a Premium plan and Consumption.

[Francisco-Gamino]

Description

Need to support switching between a Premium plan and Consumption. This was reported by a customer via twitter: https://twitter.com/Patte81/status/1192836976430452738

[jschwanz]

This and the related #11566 are very important to me.

[Francisco-Gamino]

cc: @anirudhgarg @anthonychu @eamonoreilly for FYI

[Francisco-Gamino]

Moving to Backlog. Adding @stefanushinardi and @cachai2 for FYI.