Add support for Managed Identity

[kylan11]

As of today, authentication is done either with plain connection string or accountName/accessKey string credentials.
This doesn't allow to use DefaultAzureCredential() for configured managed identity in case of enterprise applications hosted on Azure.

There should be a boolean "managedIdentity" MASOption that requires an "accountName" only.

It would appear that this change requires migrating from "BlobService" (azure-storage) to "BlobClient" (@azure/storage-blob).
There might be a way to keep BlobService by using createBlobServiceWithTokenCredential(host, TokenCredential) but it might require a bit more configuration and I didn't investigate thoroughly.

[Soggywaters]

+1 on managed identity. It is now the preferred way to connect to Azure resources as it doesn't need access keys anymore.