Add wheel url support

[Pegasust]

Fixes #1239

This adds support for pyproject.toml that has url with .whl and built with preferWheels = true.

[tool.poetry.dependencies]
my-complex-package = {url = "https://github.com/nix-user/complex-package/releases/download/complex-3.6.0/my-complex-package-3.6.0-py3-none-any.whl"}

poetry2nix's previous behavior reinstalls (by fetching from the specified url) the wheel AFTER the dependencies (including the wheel-via-url) are resolved and patched onto the Python environment from unerased wheel dependency from pyproject This is from pipInstallHook running at installPhase.

poetry2nix/mk-poetry-dep.nix

Line 120 in 5b3a515

pythonPackages.pipInstallHook

We are relaxing this install phase by having pyproject accept any version of the installed package, which should become a no-op because our materialized python already has this dependency attached with a dependencies hook within other special dep hooks that we already have.

On the topic of data science packages, we did also discover potentially unintended behavior with pytorch from #1109. We seem to require libcuda to be installed/managed separately, since ml-stack and use-url-wheel tests go through correctly in Darwin (which doesn't require CUDA!), but fails at x86_64 CI. I did added a HACK stanza on skipping this part of integration test.