[cr142] Disable ImageService now that page_image_service::kImageService feature flag is gone

We used to disable `ImageService` via the `page_image_service::kImageService`
feature flag, but that feature flag was removed recently. Instead, we should
disable `ImageService` completely by always denying consent in
`ImageServiceConsentHelper::GetConsentStatus`.

Chromium changes:
https://source.chromium.org/chromium/chromium/src/+/fdbc6e177df72cab865004e8589b067d3222d20f

commit fdbc6e177df72cab865004e8589b067d3222d20f
Author: Irina <irfedorova@google.com>
Date:   Thu Sep 25 15:03:17 2025 -0700

    [Code Health] Cleanup ImageService feature

    Fixed: 356237096
    Change-Id: Ie65e759b04b9e5ab18a643440bef4c584edb8e6d
    Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6975064
    Reviewed-by: Marlon Facey <mfacey@chromium.org>
    Reviewed-by: Caroline Rising <corising@chromium.org>
    Reviewed-by: Brandon Wylie <wylieb@google.com>
    Reviewed-by: David Roger <droger@chromium.org>
    Commit-Queue: Irina Fedorova <irfedorova@google.com>
    Reviewed-by: Adam Arcaro <adamta@google.com>
    Cr-Commit-Position: refs/heads/main@{#1520905}

chromium_src/components/page_image_service/image_service_consent_helper.cc

@@ -0,0 +1,19 @@
+/* Copyright (c) 2025 The Brave Authors. All rights reserved.
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+#include "components/sync/service/sync_service_utils.h"
+
+namespace syncer {
+bool RejectConsent() {
+  return true;
+}
+}  // namespace syncer
+
+#define GetUploadToGoogleState(...) \
+  RejectConsent() || syncer::GetUploadToGoogleState(__VA_ARGS__)
+
+#include <components/page_image_service/image_service_consent_helper.cc>
+
+#undef GetUploadToGoogleState

test/filters/components_unittests.filter

@@ -90,6 +90,11 @@
 # switches::kSyncEnableBookmarksInTransportMode
 -InitialAccountBookmarkDeduplicatorTest.*
 
+# These tests fail because we patch ImageServiceConsentHelper::GetConsentStatus
+# to return false always
+-ImageServiceConsentHelperTest.*
+-ImageServiceImplTest.*
+
 # Tests below this point have not been diagnosed or had issues created yet.
 -AccountInvestigatorTest.*
 -AccountReconcilorDiceTest.*