This commit changes from cargo2nix to just use `buildRustPackage`, which
does not generate itermediate crate derivations for the build. This
means that we lose dependency caching (for CI as well), but on the other
hand it becomes much more cacheable for people that actually use Nix to
add the dependencies.
This relies on Cargo2Nix, and because we don't want to be maintaining
that file by hand, we introduce a new continuous workflow to
automatically update the generated Cargo.nix and submit a PR whenever
something is merged into master.
This should make the process of supporting Nix bearable. We'll
re-assess in a while.
Co-authored-by: KtorZ <matthias.benkort@gmail.com>
waalge