Add prepared text layout RNTester E2E setup (#58414)

Summary:
Pull Request resolved: #58414

Add an opt-in RNTester E2E configuration that installs the prepared text layout feature-flag provider before React Native starts. An explicit `configName` selects that configuration directly, while existing tests continue to use the default configurations.

Changelog:
[Internal] - Add an opt-in RNTester E2E configuration for prepared text layout

Differential Revision: D119336370

Author: Abbondanzo

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/defaults/DefaultNewArchitectureEntryPoint.kt

@@ -88,19 +88,7 @@ public object DefaultNewArchitectureEntryPoint {
       error(errorMessage)
     }
 
-    when (releaseLevel) {
-      ReleaseLevel.EXPERIMENTAL -> {
-        ReactNativeFeatureFlags.override(
-            ReactNativeFeatureFlagsOverrides_RNOSS_Experimental_Android(),
-        )
-      }
-      ReleaseLevel.CANARY -> {
-        ReactNativeFeatureFlags.override(ReactNativeFeatureFlagsOverrides_RNOSS_Canary_Android())
-      }
-      ReleaseLevel.STABLE -> {
-        ReactNativeFeatureFlags.override(ReactNativeFeatureFlagsOverrides_RNOSS_Stable_Android())
-      }
-    }
+    ReactNativeFeatureFlags.override(getDefaultFeatureFlagsProvider())
 
     privateTurboModulesEnabled = turboModulesEnabled
     privateBridgelessEnabled = bridgelessEnabled
@@ -128,6 +116,13 @@ public object DefaultNewArchitectureEntryPoint {
     DefaultSoLoader.maybeLoadSoLibrary()
   }
 
+  internal fun getDefaultFeatureFlagsProvider(): ReactNativeFeatureFlagsProvider =
+      when (releaseLevel) {
+        ReleaseLevel.EXPERIMENTAL -> ReactNativeFeatureFlagsOverrides_RNOSS_Experimental_Android()
+        ReleaseLevel.CANARY -> ReactNativeFeatureFlagsOverrides_RNOSS_Canary_Android()
+        ReleaseLevel.STABLE -> ReactNativeFeatureFlagsOverrides_RNOSS_Stable_Android()
+      }
+
   @JvmStatic
   public val fabricEnabled: Boolean
     get() = true

packages/rn-tester/android/app/src/main/java/com/facebook/react/FBRNTesterEndToEndHelper.kt

@@ -12,6 +12,8 @@ import java.io.PrintWriter
 
 @Suppress("UNUSED_PARAMETER")
 internal object FBRNTesterEndToEndHelper {
+  fun initializeConfig(application: Application) = Unit
+
   fun onCreate(application: Application) {
     // no-op This is an empty implementation to stub out Meta's internal test coverage
     // instrumentation.

packages/rn-tester/android/app/src/main/java/com/facebook/react/uiapp/RNTesterApplication.kt

@@ -13,6 +13,7 @@ import android.app.Application
 import com.facebook.fbreact.specs.SampleLegacyModule
 import com.facebook.fbreact.specs.SampleTurboModule
 import com.facebook.react.BaseReactPackage
+import com.facebook.react.FBRNTesterEndToEndHelper
 import com.facebook.react.PackageList
 import com.facebook.react.ReactApplication
 import com.facebook.react.ReactHost
@@ -121,6 +122,9 @@ internal class RNTesterApplication : Application(), ReactApplication {
     ReactFontManager.getInstance().addCustomFont(this, "Rubik", R.font.rubik)
     ReactFontManager.getInstance().addCustomFont(this, "FiraCode", R.font.firacode)
     super.onCreate()
+    // Must run before loadReactNative so E2E-provided system properties are readable by the
+    // feature flag overrides applied during React Native startup.
+    FBRNTesterEndToEndHelper.initializeConfig(this)
     loadReactNative(this)
   }
 }