Enable Starting Sampling profile at App Startup

Summary: In Dev Settings, we used to have an `Start Sampling Profiler on init` option, which was defunct. This diff re-enables that option. We can now start the Sampling Profiler on app start

Reviewed By: yinghuitan

Differential Revision: D7022382

fbshipit-source-id: 1db85d8a324e401c71187ba5871a91abcc18acf9

ReactAndroid/src/androidTest/java/com/facebook/react/testing/ReactSettingsForTests.java

@@ -47,4 +47,9 @@ public class ReactSettingsForTests implements DeveloperSettings {
 
   @Override
   public void setRemoteJSDebugEnabled(boolean remoteJSDebugEnabled) {}
+
+  @Override
+  public boolean isStartSamplingProfilerOnInit() {
+    return false;
+  }
 }