ory-hydra: run upstream test suite
* add `subPackages` attr to build and test relevant artifacts, remove
custom `checkPhase`
* add __darwinAllowLocalNetworking, __structuredAttrs
* update comment (https://github.com/NixOS/nixpkgs/pull/502029#discussion_r3016666366)
* use `finalAttrs.src.tag` (https://github.com/NixOS/nixpkgs/pull/502029#discussion_r3016668229)
* remove `-failfast` switch (https://github.com/NixOS/nixpkgs/pull/502029#discussion_r3016669901)
* fix tests by adding `export GOFLAGS=''${GOFLAGS//-trimpath/}`
* add `postInstall` to install shell completion, update meta attrs
