Consider removing/de-prioritizing interpreter path entry and `defaultInterpreterPath` in `Create Environment` path selector

[brettcannon]

When you get asked to select a Python interpreter via Create Environment where you only have one or two interpreters, the list gets overwhelmed by the "Enter Interpreter Path" entry (are people even using it that much for Create Environment?), and if you have python.defaultInterpreterPath set then a majority of your entries now have a codicon.

We may want to re-evaluate what we show, both in Create Environment and in general, based on what people are actually using and from a perspective of Create Environment being a convenience.

[karrtikr]

We can remove the special quickpick item entries like python.defaultInterpreterPath setting value and the Enter interpreter path... item in case of create environment, I agree it doesn't need to be that sophisticated.

[karthiknadig]

In the new extension we ask the environment managers to provide environments for the purpose of creating virtual envs. We no longer show any of these settings in the new extension. Paths are handled by individual environment managers, and they can control this behavior as needed.