Add option to interact with storage API using complete URI of storage service

**Is your feature request related to a problem? Please describe.**
I am experimenting with proxy layer on top existing storage accounts. User calls for operations on storage service using the complete URL e.g. "https://storage.contosoimagesproxy.net". The proxy service in turn connects to underlying storage account e.g. "https://contosoimages1.blob.core.windows.net".

This is currently supported in `azure-sdk-for-python`. I can create client to storage service and it works out of the box as:

`service = BlobServiceClient(account_url="https://storage.contosoimagesproxy.net")`.

**Describe the solution you'd like**
Storage module should accept a parameter for complete URL of storage account as `storage-account-url`. e.g.

`az storage container list --storage-account-url "https://storage.contosoimagesproxy.net" --account-key "some_secret"`

**Describe alternatives you've considered**
NA

**Additional context**
A similar issue raised for `azure-powershell`: https://github.com/Azure/azure-powershell/issues/17285