python3.pkgs.*: Explicitly pass buildPythonPackage format parameter

Long term we should move everything over to `pyproject = true`, but in
the mean time we can work towards deprecating the implicit `format` paremeter.

cc https://github.com/NixOS/nixpkgs/issues/253154
cc @mweinelt @figsoda

pkgs/development/python-modules/coverage/default.nix

@@ -8,6 +8,7 @@
 buildPythonPackage rec {
   pname = "coverage";
   version = "7.3.1";
+  format = "setuptools";
   # uses f strings
   disabled = pythonOlder "3.5";