Move pkgs/lib/ to lib/

pkgs/lib/attrsets.nix lib/attrsets.nix
pkgs/lib/composable-derivation.nix lib/composable-derivation.nix
pkgs/lib/customisation.nix lib/customisation.nix
pkgs/lib/debug.nix lib/debug.nix
pkgs/lib/default.nix lib/default.nix
pkgs/lib/licenses.nix lib/licenses.nix
pkgs/lib/lists.nix lib/lists.nix
pkgs/lib/maintainers.nix lib/maintainers.nix
pkgs/lib/meta.nix lib/meta.nix
pkgs/lib/misc.nix lib/misc.nix
pkgs/lib/modules.nix lib/modules.nix
pkgs/lib/options.nix lib/options.nix
pkgs/lib/platforms.nix lib/platforms.nix
pkgs/lib/properties.nix lib/properties.nix
pkgs/lib/sources.nix lib/sources.nix
pkgs/lib/strings-with-deps.nix lib/strings-with-deps.nix
pkgs/lib/strings.nix lib/strings.nix
pkgs/lib/systems.nix lib/systems.nix
pkgs/lib/tests.nix lib/tests.nix
pkgs/lib/trivial.nix lib/trivial.nix
pkgs/lib/types.nix lib/types.nix