Push some logging utils for naive testing purposes

lib/android/app/src/main/java/com/reactnativenavigation/utils/Functions.java

+package com.reactnativenavigation.utils;
+
+public class Functions {
+    public interface Unit<T> {
+        T get();
+    }
+}

lib/android/app/src/main/java/com/reactnativenavigation/utils/Time.java

+package com.reactnativenavigation.utils;
+
+import android.util.Log;
+
+import java.util.HashMap;
+import java.util.Map;
+
+@SuppressWarnings("WeakerAccess")
+public class Time {
+    private static Map<String, Long> tagsToStartTime = new HashMap<>();
+    private static Now now = new Now();
+
+    public static <T> T log(String tag, Functions.Unit<T> unit) {
+        log(tag);
+        T t = unit.get();
+        log(tag);
+        return t;
+    }
+
+    public static void log(String tag) {
+        if (tagsToStartTime.containsKey(tag)) {
+            Log.i(tag, "Elapsed: " + (now() - time(tag)));
+        } else {
+            Log.i(tag, "logging start");
+        }
+        tagsToStartTime.put(tag, now());
+    }
+
+    private static long now() {
+        return now.now();
+    }
+
+    private static long time(String tag) {
+        return tagsToStartTime.get(tag);
+    }
+}