This change makes it possible to use this nix-config in all the
different ways imaginable (containers, bare metal, tests, and as a
separate flake input) *without* running into infinite recursion
issues with self.
It does this by using a trick similar to JavaScript in which
`var self = this;`, thus enabling the usage of "this" (or self, in
Nix's case) where it wouldn't otherwise be possible.
Note that this *only* works if the input for this repository is named
nix-config. This makes it impractical to combine with multiple
configurations that employ the same strategy.
This change makes it possible to import the modules that are required
from the flake inputs in the output modules themselves, thus preventing
users from having to manually import those modules.
This simplifies things overall and was made possible by the specialArgs
option that allowed these flake inputs to be passed into our container.
