Rename platform_services to platform_channel (flutter#9018)

* Rename platform_services to platform_channel

* rename in README

* renamed tests

* update modules.xml

Author: szakarias

dev/devicelab/bin/tasks/platform_services_test.dart renamed to dev/devicelab/bin/tasks/platform_channel_test.dart

@@ -13,7 +13,7 @@ import '../framework/utils.dart';
 
 TaskFunction createPlatformServiceDriverTest() {
   return new DriverTest(
-      '${flutterDirectory.path}/examples/platform_services',
+      '${flutterDirectory.path}/examples/platform_channel',
       'test_driver/button_tap.dart',
   );
 }

dev/devicelab/bin/tasks/platform_services_test_ios.dart renamed to dev/devicelab/bin/tasks/platform_channel_test_ios.dart

@@ -83,9 +83,9 @@ tasks:
     stage: devicelab
     required_agent_capabilities: ["has-android-device"]
 
-  platform_services_test:
+  platform_channel_test:
     description: >
-     Runs a driver test on the Platform Services sample app on Android.
+     Runs a driver test on the Platform Channel sample app on Android.
     stage: devicelab
     required_agent_capabilities: ["has-android-device"]
 
@@ -152,9 +152,9 @@ tasks:
 
   # iOS on-device tests
 
-  platform_services_test_ios:
+  platform_channel_test_ios:
     description: >
-      Runs a driver test on the Platform Services sample app on iOS.
+      Runs a driver test on the Platform Channel sample app on iOS.
     stage: devicelab_ios
     required_agent_capabilities: ["has-ios-device"]
 

dev/devicelab/lib/tasks/perf_tests.dart

@@ -25,7 +25,7 @@ Available examples include:
 - **Flutter gallery** The [flutter gallery app](flutter_gallery) showcases
   Flutter's implementation of [material design](https://material.google.com/).
 
-- **Platform Services** The [platform services app](platform_services)
+- **Platform Channel** The [platform channel app](platform_channel)
   demonstrates how to connect a Flutter app to platform-specific APIs. For
   documentation, see https://flutter.io/platform-channels/ .