[FEATURE REQ] Investigate XML stack for Azure.Core

[joshfree]

Tracking issue for investigating and adding a 3rd party C99 XML stack for Azure.Core usage.

Expat, a stream-orientated XML parser library written in C seems like a good place to start the investigation. "Expat excels with files too large to fit RAM, and where performance and flexibility are crucial."

https://libexpat.github.io/

[ahsonkhan]

There is no need for an XML stack, currently in the embedded SDK.

If we support storage put/commit block list, we might need this, but we can manually create the XML payload for that.