[tests] Move test suite into same repo

tests/android/app/src/main/java/com/reactnativefirebasedemo/MainActivity.java

@@ -0,0 +1,15 @@
+package com.reactnativefirebasedemo;
+
+import com.facebook.react.ReactActivity;
+
+public class MainActivity extends ReactActivity {
+
+    /**
+     * Returns the name of the main component registered from JavaScript.
+     * This is used to schedule rendering of the component.
+     */
+    @Override
+    protected String getMainComponentName() {
+        return "ReactNativeFirebaseDemo";
+    }
+}