feat: add to pypi in feature

[ruben-arts]

fixes #1133

Now you can also run:

pixi add --feature test --pypi elsie

This results in a pixi.toml to:

[feature.test.pypi-dependencies]
elsie = "*"

and in a pyproject.toml to:

[tool.pixi.feature.test.pypi-dependencies]
elsie = "*"

Note, it doesn't add it to the optional dependencies not sure if we should do that. @olivier-lacroix what do you think?

[olivier-lacroix]

Great @ruben-arts. I had wondered why there was not feature argument to add_pypi_dependency then forgot about it 🤭.

Yes, I reckon for pyproject.toml, it would make sense to add pypi dependencies to the native pyproject.toml arrays.

We should also

• refactor duplicate detection to leverage the manifest rather than the toml document (as duplicates can be in different Toml tables)
• modify dependency removal to try and remove from the various possible tables (pixi and native pyproject)

[matthewfeickert]

Thank you for adding this! I was going to open an Issue asking for it last night, but great to see it in the v0.19.0 release notes today. 🚀