[Enhancement] Switch the Azure Blob Storage client from the now deprecated azure-storage-blob-go to azure-sdk-for-go/sdk/storage/azblob

[renormalize]

Enhancement (What you would like to be added):

The currently used Azure Blob Storage client go module github.com/Azure/azure-storage-blob-go at v0.8.0 is extremely old and had been deprecated a while ago.

This dependency should be removed, and a maintained equivalent of this project, github.com/Azure/azure-sdk-for-go/sdk/storage/azblob should be used for interfacing with the Azure Blob Storage API.

Motivation (Why is this needed?):

It is long overdue to remove the dependency on the deprecated module and make use of a more up to date version of the client.

Moving to the newer client go module would enable in making use of certain features ABS offers, which are planned to be used in an upcoming release of etcd-backup-restore.