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.
ttyd hasn't seen a release in a while, but has a few useful bugfixes and
features (such as IPv6) that are good to have. It also seems to fix a
few crashes I encountered (likely due to newer openssl/libwebsockets).
So in an untraditional fashion, we'll adopt this with a _pre tag to
ensure it gets bumped correctly later on.
Signed-off-by: Austin Seipp <aseipp@pobox.com>
