benchmark: add benchmark for object properties

Adds a benchmark to compare the speed of property setting/getting in four cases:

• Dot notation: obj.prop = value
• Bracket notation with string: obj['prop'] = value
• Bracket notation with string variable: obj[prop] = value
• Bracket notation with Symbol variable: obj[sym] = value

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