stabilizing gradle-env{.json,.nix} format/interface

[ghost]

Since we had the discussion on breaking changes in NixOS/nixpkgs#77422 I've kind of been waiting for a 1.0.0 release in the assumption that there might be more breaking changes until then. So I would like to track the status of this stabilization here. What is still to be done, or can we use gradle2nix in nixpkgs as-is?

[tadfisher]

Packaging gradle2nix should be fine, so I would start with that.

I sort of disagree with integrating the buildGradle function in nixpkgs. We don't do that for node2nix, for example, which gives node2nix the freedom to change their lockfile format. So I'd prefer we didn't do that, and just package both gradle-env.nix and gradle-env.json with each derivation that needs them.

[tadfisher]

One incompatible change I want to make is to switch to SRI hashes, so I will likely rename the sha256 field for dependency objects.