napi: improve runtime performance of every napi fun call.

napi: improve runtime performance of every napi fun call.

Added a new struct CallbackBundle to eliminate all GetInternalField() calls.

The principle is to store all required data inside a C++ struct, and then store the pointer in the JavaScript object. Before this change, the required data are stored in the JavaScript object in 3 or 4 seperate pointers. For every napi fun call, 3 of them have to be fetched out, which are 3 GetInternalField() calls; after this change, the C++ struct will be directly fetched out by using v8::External::Value(), which is faster.

Profiling data show that GetInternalField() is slow. On an i7-4770K (3.50GHz) box, a C++ V8-binding fun call is 8 ns, before this change, napi fun call is 36 ns; after this change, napi fun call is 20 ns.

The above data are measured using a modified benchmark in 'benchmark/misc/function_call'. The modification adds an indicator of the average time of a "chatty" napi fun call (max 50M runs). This change will speed up chatty case 1.8x (overall), and will cut down the delay of napi mechanism to approx. 0.5x.

Background: a simple C++ binding function (e.g. receiving little from JS, doing little and returning little to JS) is called 'chatty' case for JS<-->C++ fun call routine.

This improvement also applies to getter/setter fun calls.

Checklist

• make -j4 test (UNIX), or vcbuild test (Windows) passes
• tests and/or benchmarks are included
• commit message follows commit guidelines