We were incorrectly handling `IOExceptions` thrown by
the `InputStream` side of the upload operation, resulting
in a `ClassCastException` as we expected to never get
`IOException` from the Azure SDK code but we do in practice.
This PR also sets an assertion on `markSupported` for the
streams used by the SDK as adding the test for this scenario
revealed that the SDK client would retry uploads for
non-mark-supporting streams on `IOException` in the `InputStream`.