Include `Proxy`-less use of `Object.hasOwn` as a mitigation

The project already covers using `Object.hasOwn` as a mitigation through the [`Proxy`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Proxy)-based mitigations. However, especially w.r.t. performance benchmarks this might not give the full picture of which mitigation is appropriate for any given situation - presumably just calling `Object.hasOwn` is more performant than using a `Proxy`. As such, ideally the mitigation of just using `Object.hasOwn` before accessing a property is covered as a mitigation for testing, benchmarking, and [mitigation description](https://github.com/ericcornelissen/prototype-pollution-mitigation-tests/tree/1331716c1c28e7714cbbaa3683c5f00dc0fc43b0#mitigations).