Sort available environments by assumed usefulness

[kimadeline]

1. Local environments, i.e. .venv
2. Globally stored environments, e.g. $WORK_ON
3. Global installs, e.g. /usr/bin/python3.9

Always sort with newest version of Python first within each subgroup.

Design document at https://github.com/microsoft/vscode-python/wiki/Sort-environments-by-assumed-usefulness

[luabud]

Another good side effect here is that I think the "default macOS interpreter isn't great" notification would not happen anymore on the first run experience, as it wouldn't be auto selected (#3843)