[ReactNative] Improvements on perf measurement output

Summary:
I updated the logging a bit to sum up the time spent in render methods (product code) and the total React time, and then cleaned up some of the other console.logs. I also stopped printing out the majority of React perf output, since it's pretty large and not super useful to print on every load.

I chatted with Jordan a while ago about whether the time between componentDidMount and requestAnimationFrame is a good estimate for how long it takes for React to serialize changes across the bridge and render on the native side, and it sounded like it was a reasonable approximation. I added this to the logging as well, using RCTRenderingPerf still so that it won't console.log when performance measurement isn't enabled.

The total output now looks like: https://phabricator.fb.com/P19764547
If I add up fetch time, relay time, total time spent in React, and time to render across the bridge, I get 915ms out of the total 964ms, although "Total Relay time" and "Total time spent in React" probably has some overlap.

Test Plan:
Sample output: https://phabricator.fb.com/P19764547
Also ran with perf turned off, no errors

Libraries/Utilities/RCTRenderingPerf.js

@@ -37,6 +37,19 @@ var RCTRenderingPerf = {
     ReactDefaultPerf.stop();
     ReactDefaultPerf.printInclusive();
     ReactDefaultPerf.printWasted();
+
+    var totalRender = 0;
+    var totalTime = 0;
+    var measurements = ReactDefaultPerf.getLastMeasurements();
+    for (var ii = 0; ii < measurements.length; ii++) {
+      var render = measurements[ii].render;
+      for (var nodeName in render) {
+        totalRender += render[nodeName];
+      }
+      totalTime += measurements[ii].totalTime;
+    }
+    console.log('Total time spent in render(): ' + totalRender + 'ms');
+
     perfModules.forEach((module) => module.stop());
   },