[DEVOPS-1083] lib.nix: Simplify forEnvironments and add comments
[DEVOPS-1083] lib.nix: Simplify forEnvironments and add comments

input-output-hk/cardano-sl,input-output-hk/cardano-sl,input-output-hk/cardano-sl,input-output-hk/cardano-sl,input-output-hk/pos-haskell-prototype,input-output-hk/pos-haskell-prototype,input-output-hk/pos-haskell-prototype