Refine `check-owner`

[Malix-Labs]

Check if the nixpkgs repository is exactly the GitHub repository NixOS/nixpkgs (not only belongs to @NixOS), regardless of the flake reference type (github, git, tarball, …)

Also include hydra's

• https://channels.nixos.org/<CHANNEL>/nixexprs.tar.xz
• https://releases.nixos.org/<VERSION>/<CHANNEL>/<REV>/nixexprs.tar.xz
• Perhaps more links I'm not aware of

Also see https://discourse.nixos.org/t/questions-about-inputs-nixpkgs/69095/14?u=malix

[Malix-Labs]

Well actually, because the URL points directly to a compressed archive, Nix records this dependency in flake.lock as a tarball node type rather than a Git repository node type

Which is skipped entirely for this option

https://github.com/DeterminateSystems/flake-checker/blob/ec67ebf5b7a666b3509006c3e2ce5e7dfbcaaf38/src/condition.rs#L36-L45

https://github.com/DeterminateSystems/flake-checker/blob/ec67ebf5b7a666b3509006c3e2ce5e7dfbcaaf38/src/flake.rs#L88-L97