perf(ReactBridge): Minor improvement to batch processing perf (#819)
perf(ReactBridge): Minor improvement to batch processing perf (#819)

Previously, the batch processing step converted the entire list of module IDs and method IDs from the flushed queue into arrays. This involved the allocation of an array. This approach only requires the conversion from a Newtonsoft.Json number (I suspect the internal representation is double) to an integer.

I ran a small test script in a ConsoleApp to ensure this was actually a performance improvement:
```c#
var size = 100;
var repeat = 1000;
var values = Enumerable.Range(0, size);
var json = $"[[{string.Join(",",values)}],[{string.Join(",",values)}],[{string.Join(",", values.Select(_ => "[]"))}]]";
var jarr = JArray.Parse(json);

var x = 0;

GC.Collect();
GC.WaitForPendingFinalizers();

var sw = Stopwatch.StartNew();
for (var i = 0; i < repeat; ++i)
{
    var moduleIds = jarr[0].ToObject<int[]>();
    var methodIds = jarr[1].ToObject<int[]>();
    var arguments = (JArray)jarr[2];
    for (var j = 0; j < moduleIds.Length; ++j)
    {
        var moduleId = moduleIds[j];
        var methodId = methodIds[j];
        var argInst = (JArray)arguments[j];
        Call(moduleId, methodId, argInst);
    }
}
Console.WriteLine("Elapsed: {0} ms", sw.Elapsed.TotalMilliseconds);

GC.Collect();
GC.WaitForPendingFinalizers();

sw.Restart();
for (var i = 0; i < repeat; ++i)
{
    var moduleIds = (JArray)jarr[0];
    var methodIds = (JArray)jarr[1];
    var arguments = (JArray)jarr[2];
    for (var j = 0; j < moduleIds.Count; ++j)
    {
        var moduleId = moduleIds[j].Value<int>();
        var methodId = methodIds[j].Value<int>();
        var argInst = (JArray)arguments[j];
        Call(moduleId, methodId, argInst);
    }
}
Console.WriteLine("Elapsed: {0} ms", sw.Elapsed.TotalMilliseconds);

```

In this case, `Call` was just a no-op, but the performance without deserializing into an array had about a 10x improvement (for a batch size of 100, which I suspect is a bit too large).  For smaller batch sizes (batches of 10), the performance improvement was 40x.
lbochenek/react-native-windows,lbochenek/react-native-windows,lbochenek/react-native-windows,lbochenek/react-native-windows