nixos/systemd: Don't use apply for $PATH

When not using apply, other modules can use $PATH as a list instead of
getting a colon-separated list to each /bin directory.

nixos/doc/manual/release-notes/rl-2009.xml

@@ -777,6 +777,11 @@ CREATE ROLE postgres LOGIN SUPERUSER;
      <link xlink:href="https://github.com/NixOS/nixpkgs/pull/63103">PR #63103</link>.
     </para>
    </listitem>
+   <listitem>
+    <para>
+      <literal>config.systemd.services.${name}.path</literal> now returns a list of paths instead of a colon-separated string.
+    </para>
+   </listitem>
   </itemizedlist>
  </section>
 

nixos/modules/system/boot/systemd-unit-options.nix

@@ -234,7 +234,6 @@ in rec {
     path = mkOption {
       default = [];
       type = with types; listOf (oneOf [ package str ]);
-      apply = ps: "${makeBinPath ps}:${makeSearchPathOutput "bin" "sbin" ps}";
       description = ''
         Packages added to the service's <envar>PATH</envar>
         environment variable.  Both the <filename>bin</filename>

nixos/modules/system/boot/systemd.nix

@@ -257,7 +257,7 @@ let
               pkgs.gnused
               systemd
             ];
-          environment.PATH = config.path;
+          environment.PATH = "${makeBinPath config.path}:${makeSearchPathOutput "bin" "sbin" config.path}";
         }
         (mkIf (config.preStart != "")
           { serviceConfig.ExecStartPre =