nodePackages: add meta.mainProgram to packages with multiple executables
nodePackages: add meta.mainProgram to packages with multiple executables

where none of the executables match the package's `name` or `pname`, and
one of the executables is the obvious `mainProgram`.

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