libgpiod's Python bindings no longer worked after the upgrade to 2.0.1. The
build system installs an egg, which doesn't work in nixpkgs. To fix this, I
adopted the same approach I took in #204884. This patch builds the Python
bindings as a separate package, using the normal nixpkgs Python infrastructure.
Besides fixing the bindings, this has the added benefit of avoiding the need to
build a redundant copy of libgpiod as part of the Python bindings package.
Lastly, I cleaned up the libgpiod package a bit, removing an unused dependency
on kmod and an unnecessary configure flag. I also added the full list of
licenses that apply to the package.
continuation of #109595
pkgconfig was aliased in 2018, however, it remained in
all-packages.nix due to its wide usage. This cleans
up the remaining references to pkgs.pkgsconfig and
moves the entry to aliases.nix.
python3Packages.pkgconfig remained unchanged because
it's the canonical name of the upstream package
on pypi.
