Add Hermes support to React Native on Android (#25613)

Summary:
Yesterday we shipped hermesengine.dev as part of the current 0.60 release. This PR brings those changes to master.

## Changelog

[General] [Added] - Added support for Hermes
Pull Request resolved: https://github.com/facebook/react-native/pull/25613

Test Plan:
* CI is green both on GitHub and at FB
* Creating a new app from source can use Hermes on Android

Reviewed By: cpojer

Differential Revision: D16221777

Pulled By: willholen

fbshipit-source-id: aa6be10537863039cb666292465ba2e1d44b64ef

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

@@ -10,6 +10,7 @@ import static com.facebook.react.modules.systeminfo.AndroidInfoHelpers.getFriend
 import android.app.Activity;
 import android.app.Application;
 import androidx.annotation.Nullable;
+import com.facebook.hermes.reactexecutor.HermesExecutorFactory;
 import com.facebook.infer.annotation.Assertions;
 import com.facebook.react.bridge.JSBundleLoader;
 import com.facebook.react.bridge.JSIModulePackage;
@@ -24,6 +25,7 @@ import com.facebook.react.jscexecutor.JSCExecutorFactory;
 import com.facebook.react.modules.core.DefaultHardwareBackBtnHandler;
 import com.facebook.react.packagerconnection.RequestHandler;
 import com.facebook.react.uimanager.UIImplementationProvider;
+import com.facebook.soloader.SoLoader;
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Map;
@@ -260,7 +262,7 @@ public class ReactInstanceManagerBuilder {
         mCurrentActivity,
         mDefaultHardwareBackBtnHandler,
         mJavaScriptExecutorFactory == null
-            ? new JSCExecutorFactory(appName, deviceName)
+            ? getDefaultJSExecutorFactory(appName, deviceName)
             : mJavaScriptExecutorFactory,
         (mJSBundleLoader == null && mJSBundleAssetUrl != null)
             ? JSBundleLoader.createAssetLoader(
@@ -281,4 +283,15 @@ public class ReactInstanceManagerBuilder {
         mJSIModulesPackage,
         mCustomPackagerCommandHandlers);
   }
+
+  private JavaScriptExecutorFactory getDefaultJSExecutorFactory(String appName, String deviceName) {
+    try {
+      // If JSC is included, use it as normal
+      SoLoader.loadLibrary("jscexecutor");
+      return new JSCExecutorFactory(appName, deviceName);
+    } catch (UnsatisfiedLinkError jscE) {
+      // Otherwise use Hermes
+      return new HermesExecutorFactory();
+    }
+  }
 }