grafana: 7.5.7 -> 8.0.0
grafana: 7.5.7 -> 8.0.0

ChangeLog: https://github.com/grafana/grafana/releases/tag/v8.0.0

Also had to skip one of the plugin tests as it tried to access
grafana.com (test-failure is documented as comment in `preBuild`).

NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs