Move iOS ImageFetcher to ios/web/public

ios/web/BUILD.gn

Index: ios/web/BUILD.gn
diff --git a/ios/web/BUILD.gn b/ios/web/BUILD.gn
index 8c6aa555ca144e9b3501eba94e2835891c94f41a..6a6ba6fe7985ac6500c7597df834d849a9379ab9 100644
--- a/ios/web/BUILD.gn
+++ b/ios/web/BUILD.gn
@@ -363,6 +363,7 @@ source_set("test_support") {
     "//ios/testing:ios_test_support",
     "//ios/testing:ocmock_support",
     "//ios/third_party/gcdwebserver",
+    "//ios/web/public/image_fetcher",
     "//ios/web/test:mojo_bindings",
     "//net:test_support",
     "//testing/gmock",
@@ -380,6 +381,8 @@ source_set("test_support") {
     "public/test/http_server_util.mm",
     "public/test/js_test_util.h",
     "public/test/js_test_util.mm",
+    "public/test/mock_image_data_fetcher.h",
+    "public/test/mock_image_data_fetcher.mm",
     "public/test/native_controller_test_util.h",
     "public/test/native_controller_test_util.mm",
     "public/test/navigation_test_util.h",
@@ -478,6 +481,7 @@ test("ios_web_unittests") {
     "//base/test:test_support",
     "//ios/net",
     "//ios/testing:ocmock_support",
+    "//ios/web/public/image_fetcher:unit_tests",
     "//ios/web/test:mojo_bindings",
     "//net:test_support",
     "//services/service_manager/public/cpp",