[Text Analytics] Enable test suite to choose between AAD and APIKey

[deyaaeldeen]

We need to be able to work with an endpoint that we are not authorized to authenticate using AAD with. Using a dev endpoint is an example of such scenario. I think we can default to ADD and we can switch to API Key using an environment variable. Perhaps other packages would want to do something else so reach out to them.

[deyaaeldeen]

This has been resolved now since we use the matrix function to test both AAD and APIKey.