Detect and allow selecting of PyPy environments

[brettcannon]

on Windows the pattern is like below, and seems "missed"

pypy3.7-v7.3.5rc3-win64\pypy3.exe
pypy3.7-v7.3.5-win64\pypy3.exe

indeed, I have parametrized "settings.json" like this

{ 
"python.interpreterPath": "${env:WINPYDIR}\\\\pypy3.exe", 
"jupyter.widgetScriptSources": [ 
"jsdelivr.com", 
"unpkg.com" 
], 
} 

.... pypy3.exe is not said "found"

if I copy "pypy3.exe" to "python.exe" ... miracle (greuuuuuuuuh)

I would suppose the problem is in there ?

https://github.com/microsoft/vscode-python/blob/main/src/client/pythonEnvironments/discovery/locators/services/pyenvLocator.ts

Originally posted by @stonebig in a discussion

[brettcannon]

Moved to #17202