ambient: Move policy handler code to ash ambient directory

This CL moves the code the code related to the managed screensaver out
of the c/b/ash/policy directory. This directory should only contain policy core framework code.

A follow up CL will instantiate the policy handler service in Shell, along with the Ambient Controller.

Bug: b:278873241
Test: ./ash_unittests --gtest_filter=ScreensaverImagesPolicyHandlerTest.*
Test: ./ash_unittests --gtest_filter=ScreensaverImageDownloaderTest.*

Change-Id: I4267d7baabd2faa49b646d4d98aab0cec3edb398
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4474193
Reviewed-by: Nicolas Ouellet-Payeur <[email protected]>
Code-Coverage: Findit <[email protected]>
Reviewed-by: Dominic Battre <[email protected]>
Reviewed-by: Mitsuru Oshima <[email protected]>
Reviewed-by: Roman Sorokin <[email protected]>
Reviewed-by: Xiaohui Chen <[email protected]>
Commit-Queue: Emmanuel Arias Soto <[email protected]>
Cr-Commit-Position: refs/heads/main@{#1135938}
diff --git a/ash/ash_prefs.cc b/ash/ash_prefs.cc
index 97b8058d..9f690b3 100644
--- a/ash/ash_prefs.cc
+++ b/ash/ash_prefs.cc
@@ -7,6 +7,7 @@
 #include "ash/accessibility/accessibility_controller_impl.h"
 #include "ash/accessibility/magnifier/docked_magnifier_controller.h"
 #include "ash/ambient/ambient_controller.h"
+#include "ash/ambient/managed/screensaver_images_policy_handler.h"
 #include "ash/app_list/app_list_controller_impl.h"
 #include "ash/assistant/assistant_controller_impl.h"
 #include "ash/calendar/calendar_controller.h"
@@ -121,6 +122,7 @@
   PrivacyScreenController::RegisterProfilePrefs(registry);
   ProjectorControllerImpl::RegisterProfilePrefs(registry);
   quick_pair::Mediator::RegisterProfilePrefs(registry);
+  ScreensaverImagesPolicyHandler::RegisterPrefs(registry);
   ShelfController::RegisterProfilePrefs(registry);
   SnoopingProtectionController::RegisterProfilePrefs(registry);
   TabletModeTuckEducation::RegisterProfilePrefs(registry);