Display Flake input details and diff changes

[tomberek]

Flake evaluations and jobsets are blank: https://hydra.nixos.org/build/144582512#tabs-buildinputs https://hydra.nixos.org/eval/1674817#tabs-inputs

This is probably due to the inputs being managed by the flakes' lock system, instead of needing Hydra to keep track, but it doesn't look like the information is exposed. It would be pleasant to have some flake inputs displayed, similar to: https://hydra.nixos.org/eval/1697285#tabs-inputs

Perhaps even the diff changes: https://hydra.nixos.org/api/scmdiff?rev1=23485f23ff8536592b5178a5d244f84da770bc87&branch=&uri=https%3A%2F%2Fgithub.com%2FNixOS%2Fnixpkgs.git&rev2=253aecf69ed7595aaefabde779aa6449195bebb7&type=git

[tomberek]

Something like this would be a start: https://github.com/NixOS/hydra/commit/ced0a4658f207c8a3a1552cdab682ee1d5a29cf0

I didn't quite see exactly where to ensure the "inputs" are captured and reported in a similar manner.