Reorganise sample into debug/release flavours

Summary:
This makes use of the new no-op package and also structures the app
into release and debug flavours that can be built with and without
Flipper part of the APK.

This was a pretty tedious adventure. I may have missed some corner cases
and also restructured a bunch of seemingly unrelated stuff that was
necessary to respect buck module boundaries.

Reviewed By: jknoxville

Differential Revision: D15148004

fbshipit-source-id: bf81f45105f5f16d17daccb3e8050ee00d69fc35

android/no-op/src/main/java/com/facebook/flipper/android/diagnostics/FlipperDiagnosticActivity.java

@@ -0,0 +1,12 @@
+/*
+ *  Copyright (c) 2018-present, Facebook, Inc.
+ *
+ *  This source code is licensed under the MIT license found in the LICENSE
+ *  file in the root directory of this source tree.
+ *
+ */
+package com.facebook.flipper.android.diagnostics;
+
+import android.app.Activity;
+
+public class FlipperDiagnosticActivity extends Activity {}