Use black profile with isort to reduce manual work

[mshafer-NI]

I've learned that isort now has a black profile allowing it to play nicely with black.

To start investigating bringing flake8-isort in, I opted to first test what configurations we would need to match our current style.

Changing to configuring the call to isort within _sort_imports removes the need for the custom logic around splitting multi-import lines, so choosing to contribute this simplification at this point.