nixos/udev: switch `networking.usePredicatableInterfaceNames` to a kernel param

The udev rules we are shipping no longer work with systemd v242 and were
remove upstream some time ago. It seems like the entire renaming is now
done in C and not in the udev rules.

nixos/modules/services/hardware/80-net-setup-link.rules

@@ -1,13 +0,0 @@
-# Copied from systemd 203.
-ACTION=="remove", GOTO="net_name_slot_end"
-SUBSYSTEM!="net", GOTO="net_name_slot_end"
-NAME!="", GOTO="net_name_slot_end"
-
-IMPORT{cmdline}="net.ifnames"
-ENV{net.ifnames}=="0", GOTO="net_name_slot_end"
-
-NAME=="", ENV{ID_NET_NAME_ONBOARD}!="", NAME="$env{ID_NET_NAME_ONBOARD}"
-NAME=="", ENV{ID_NET_NAME_SLOT}!="", NAME="$env{ID_NET_NAME_SLOT}"
-NAME=="", ENV{ID_NET_NAME_PATH}!="", NAME="$env{ID_NET_NAME_PATH}"
-
-LABEL="net_name_slot_end"

nixos/modules/services/hardware/udev.nix

@@ -116,10 +116,6 @@ let
         exit 1
       fi
 
-      ${optionalString config.networking.usePredictableInterfaceNames ''
-        cp ${./80-net-setup-link.rules} $out/80-net-setup-link.rules
-      ''}
-
       # If auto-configuration is disabled, then remove
       # udev's 80-drivers.rules file, which contains rules for
       # automatically calling modprobe.
@@ -282,6 +278,8 @@ in
 
     services.udev.path = [ pkgs.coreutils pkgs.gnused pkgs.gnugrep pkgs.utillinux udev ];
 
+    boot.kernelParams = mkIf (!config.networking.usePredictableInterfaceNames) [ "net.ifnames=0" ];
+
     environment.etc =
       [ { source = udevRules;
           target = "udev/rules.d";