WIP Add `v8.getHeapObjectStatistics()`

Hi!

I'd like to propose adding a implementation of Isolate::GetHeapObjectStatisticsAtLastGC() into v8 module (this is WIP).

BTW, quick question: Is there any way to "register" char* properties, the way it is right now will only work with numerical values:

#define V(index, name, _) buffer[index] = static_cast<double>(s.name());
  HEAP_WHATEVER_STATISTICS_PROPERTIES(V)
#undef V

Checklist

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