Feature: Add support for authentication with Managed Identities

[jcerjak]

Which service(blob, file, queue, table) does this issue concern?

blob

Which version of the SDK was used?

any

What's the PHP/OS version?

any

What problem was encountered?

As a developer, I would like to connect to Azure Storage by using Managed Identities, so that I can connect more securely and avoid having to manually manage SAS token life cycle.

Steps to reproduce the issue?

Have you found a mitigation/solution?

Is there a failing request ID related to this problem returned by server? What is it?

What is the storage account name and time frame of your last reproduce? (UTC YYYY/MM/DD hh:mm:ss)

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