Eager initialize Fabric in RN VR apps

Summary:
Enable eager intialization of FabricUIManager during intiialization of React Native.
This feature highly improved TTRC in Markeptlace Home

changelog: [internal] internal

Reviewed By: genkikondo

Differential Revision: D33585099

fbshipit-source-id: 0ffbc720bcb1edd1b04180189a52c82e9e2fa800

Author: mdvacca

ReactAndroid/src/main/java/com/facebook/react/ReactInstanceManager.java

@@ -1390,7 +1390,7 @@ private ReactApplicationContext createReactContext(
           mJSIModulePackage.getJSIModules(
               reactContext, catalystInstance.getJavaScriptContextHolder()));
     }
-    if (ReactFeatureFlags.eagerInitializeFabric) {
+    if (ReactFeatureFlags.enableFabricRenderer) {
       catalystInstance.getJSIModule(JSIModuleType.UIManager);
     }
     if (mBridgeIdleDebugListener != null) {

ReactAndroid/src/main/java/com/facebook/react/config/ReactFeatureFlags.java

@@ -64,9 +64,6 @@ public class ReactFeatureFlags {
   /** This feature flag enables logs for Fabric */
   public static boolean enableFabricLogs = false;
 
-  /** Feature flag to configure eager initialization of Fabric */
-  public static boolean eagerInitializeFabric = false;
-
   /** Enables Static ViewConfig in RN Android native code. */
   public static boolean enableExperimentalStaticViewConfigs = false;