Add experimental programmatic API for Monty

[yangdanny97]

Summary

For https://www.github.com/pydantic/monty/pull/501

Something about how Monty can't depend on a crate that's a GH revision hash.

I guess after this gets merged you guys need to publish it, but IDK how to do that

Test Plan

I ran all the tests at some point but after the demise of my Macbook Pro I now use a Macbook Air which has no fans so I'm reluctant to risk running the test suite and overheating it

so, TLDR trust CI

[meta-codesync]

This pull request has been imported. If you are a Meta employee, you can view this in D119299371. (Because this pull request was imported automatically, there will not be any future comments.)

[kinto0]

somewhat confusing API for an unclear use-case. if we ever merge something like this, I think it needs to be simple and have clear documentation.

I also don't see a disclaimer that this is experimental anywhere in the code

[yangdanny97]

In my view this is in the same category as glean's API or the WASM stuff, where it should be undocumented until we refine the API enough and decide to publicize it

The main purpose of merging it is so that Monty can actually release a version that uses Pyrefly

[yangdanny97]

Cleaned up a few things

[github-actions]

According to mypy_primer, this change doesn't affect type check results on a corpus of open source code. ✅

[kinto0]

Review automatically exported from Phabricator review in Meta.