Support `--with-requirements script.py` to include inline dependency metadata from another script

[blueraft]

Summary

Closes #6542

Test Plan

cargo test

[zanieb]

That was more straight-forward than I assumed! I think we'll need to align on the interface.

[T-256]

• Also consider it for uv run: https://github.com/astral-sh/uv/issues/7032

[zanieb]

@blueraft I wonder if we can push this forward? I think support in --with-requirements might make sense still, given we read a bunch of other file types there. I wonder if we can just sniff for a PEP 723 inline metadata entry in the script if there's no file extension?

[blueraft]

I wonder if we can just sniff for a PEP 723 inline metadata entry in the script if there's no file extension?

Yeah, I think we could do that. Let me give that a try!

[zanieb]

Thank you so much for your patience here!