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.
Refs #90840.
The check phase is now enabled. All tests pass on my machine.
I realized while doing this bump that igraph vendors OpenBLAS, ARPACK,
and GLPK. We can use our versions instead, and igraph builds
successfully, but 34 tests fail. I'm choosing correctness instead of
build times.
