[Feature request] Enhance handling of multiple Python environments.

[LexiconCode]

Is your feature request related to a problem? Please describe.
It's frustrating working with multiple Python environments. In order to handle these cases one has to alter executor map and other settings to handle the different python environments.

You can get partway there with workspace variables. This assumes the paths are the same per virtual environment and project and does not handle multiple non-virtualized interpreters.

Describe the solution you'd like

There's a few ways this problem could be approached.

• Extensions such as Python by Microsoft support selecting a interpreter. Code runner detect which python interpreter is an selected this would work for both virtualized and non-virtualized environments and fall back the default Python interpreter the Microsoft extension is not detected.

• Code runner could detect the Python environments (on and off sys path) or virtual environments within the workspace. The interpreter could be selectable in the settings or bottom toolbar of VS code

The following PR #915 may partially resolve this issue using the first approach.