dockerTools: Allow omitting all store paths

Adds includeStorePaths, allowing the omission of the store paths.
You generally want to leave it on, but tooling may disable this
to insert the store paths more efficiently via other means, such
as bind mounting the host store.

(cherry picked from commit 5259d66b7487b94233821e28aafb0683ae3f1df6)

pkgs/build-support/docker/examples.nix

@@ -516,4 +516,29 @@ rec {
     bash
     layeredImageWithFakeRootCommands
   ];
+
+  helloOnRoot = pkgs.dockerTools.streamLayeredImage {
+    name = "hello";
+    tag = "latest";
+    contents = [
+      (pkgs.buildEnv {
+        name = "hello-root";
+        paths = [ pkgs.hello ];
+      })
+    ];
+    config.Cmd = [ "hello" ];
+  };
+
+  helloOnRootNoStore = pkgs.dockerTools.streamLayeredImage {
+    name = "hello";
+    tag = "latest";
+    contents = [
+      (pkgs.buildEnv {
+        name = "hello-root";
+        paths = [ pkgs.hello ];
+      })
+    ];
+    config.Cmd = [ "hello" ];
+    includeStorePaths = false;
+  };
 }