Re-add support for pyenv shims

[charliermarsh]

Summary

By running get_interpreter_info.py outside of the current working directory, we seem to have broken pyenv shims.

Closes #2488.

Test Plan

Without this change (resolving to the Homebrew Python, even though we start with a shim):

DEBUG Starting interpreter discovery for Python @ `python3.11`
DEBUG Probing interpreter info for: /Users/crmarsh/.pyenv/shims/python3.11
DEBUG Found Python 3.11.7 for: /Users/crmarsh/.pyenv/shims/python3.11
Using Python 3.11.7 interpreter at: /opt/homebrew/opt/python@3.11/bin/python3.11
Creating virtualenv at: .venv
INFO Removing existing directory
Activate with: source .venv/bin/activate

With this change:

DEBUG Starting interpreter discovery for Python @ `python3.11`
DEBUG Probing interpreter info for: /Users/crmarsh/.pyenv/shims/python3.11
DEBUG Found Python 3.11.1 for: /Users/crmarsh/.pyenv/shims/python3.11
Using Python 3.11.1 interpreter at: /Users/crmarsh/.pyenv/versions/3.11.1/bin/python3.11
Creating virtualenv at: .venv
INFO Removing existing directory
Activate with: source .venv/bin/activate

[charliermarsh]

I'll look into adding a test for this: #2504