benchmark: obj property access benchmark

Benchmark that compares the obj property access patterns being used in core today. Specifically comparing the two patterns:

function A() {};
function B() {};
var obj = {A, B, C: 1};

and

function A() {}
function B() {}
var obj = {};
obj.A = A;
obj.B = B;
obj.C = 1;

@mscdex @nodejs/benchmarking

Checklist

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

Affected core subsystem(s)

benchmark