Make constructor arg of ReactContextBaseJavaModule @nullable

Summary:
ExceptionManagers are created before the `ReactApplicationContext`. Once we make them all TurboModule-compatible, they'll also subclasses `ReactContextBaseJavaModule`. This means that they'll need to be created with `ReactApplicationContext`. Since one isn't available, we'll have to call `super(null)` in their constructor.

Changelog:
[Android][Changed] - Make ReactApplicationContext nullable as the constructor argument of ReactContextBaseJavaModule

Reviewed By: PeteTheHeat

Differential Revision: D18935950

fbshipit-source-id: a643a10a42cf36a2a2d6fde87795965f16295d43

Author: RSNara

ReactAndroid/src/main/java/com/facebook/react/bridge/ReactContextBaseJavaModule.java

@@ -10,7 +10,6 @@
 import static com.facebook.infer.annotation.ThreadConfined.ANY;
 
 import android.app.Activity;
-import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
 import com.facebook.common.logging.FLog;
 import com.facebook.infer.annotation.Assertions;
@@ -28,7 +27,7 @@ public ReactContextBaseJavaModule() {
     mReactApplicationContext = null;
   }
 
-  public ReactContextBaseJavaModule(@NonNull ReactApplicationContext reactContext) {
+  public ReactContextBaseJavaModule(@Nullable ReactApplicationContext reactContext) {
     mReactApplicationContext = reactContext;
   }