Improvements for Python binary resolution

[cnpryer]

Following up on #335.

• Use the implementation for Venv.create() to search the system for a Python binary to use to generate a venv with.
• Optional Refactor the implementation for less redundant walking.
• Optional Refactor the implementation for generic recursive path searching.
• Optional Add recursion limit for walking dirs.

[messense]

Have you seen https://github.com/brettcannon/python-launcher? In maturin we also need to resolve Python binary location, it would be great if we can make python-launcher support Windows then reuse its code.

docs: https://docs.rs/python-launcher/1.0.0/python_launcher/

[cnpryer]

Definitely willing to check it out. Thanks for sharing!

[cnpryer]

Toolchains somewhat resolve this