Rename `integration_tests/external_ui` but do not touch anything else... (#142238)

Part of https://github.com/flutter/flutter/issues/142178.

dev/devicelab/lib/tasks/integration_tests.dart

@@ -42,7 +42,7 @@ TaskFunction createIntegrationTestFlavorsTest({Map<String, String>? environment}
 
 TaskFunction createExternalUiFrameRateIntegrationTest() {
   return DriverTest(
-    '${flutterDirectory.path}/dev/integration_tests/external_ui',
+    '${flutterDirectory.path}/dev/integration_tests/external_textures',
     'lib/frame_rate_main.dart',
   ).call;
 }

dev/integration_tests/external_ui/android/app/src/main/AndroidManifest.xml → dev/integration_tests/external_textures/android/app/src/main/AndroidManifest.xml

@@ -9,7 +9,7 @@ found in the LICENSE file. -->
 
     <application
         android:name="${applicationName}"
-        android:label="external_ui">
+        android:label="external_textures">
         <activity
             android:name=".MainActivity"
             android:launchMode="singleTop"

dev/integration_tests/external_ui/pubspec.yaml → dev/integration_tests/external_textures/pubspec.yaml

-name: external_ui
-description: A test of Flutter integrating external UIs.
+name: external_textures
+description: A test of Flutter integrating external textures.
 
 environment:
   sdk: '>=3.2.0-0 <4.0.0'