Upgrade to .Net SDK v12

[Jeavon]

This looks like it's going to require significant refactoring.

A useful guide for migration - https://elcamino.cloud/articles/2020-03-30-azure-storage-blobs-net-sdk-v12-upgrade-guide-and-tips.html

[Shazwazza]

Hi all, just wondering about these 2 dependencies that are listed on the current 3 beta (https://www.nuget.org/packages/UmbracoFileSystemProviders.Azure/3.0.0-beta1):

Microsoft.Azure.KeyVault.Core (>= 3.0.3)
Microsoft.Data.Services.Client (>= 5.8.4)

The keyvault dependency https://www.nuget.org/packages/Microsoft.Azure.KeyVault.Core/ has been replaced with newer APIs too. Not sure about the Microsoft.Data.Services.Client one or why that one is needed. It seems that all Azure based APIs should be using Azure.* prefixed packages?

[Jeavon]

Thanks @Shazwazza I'll have a look at those and update or remove

[Jeavon]

@Shazwazza have removed from beta2