Use URL when available natively

[iambalaam]

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This is my first attempt to solve Cannot clone a URL in Node >= 10 #109 .

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I have had to clone the property descriptors of Symbols, and I assume I should do the same for property names.

When running the following code I found that the value wasn't a primitive. This made the URL object clone to a new object, but the URLSearchParams inside it point to the same instance. (I have not assessed the performance implications of this.)

> const url = new URL('https://example.com/?a=1');
> const querySymbol = Object.getOwnPropertySymbols(url)[1] // Symbol(query)
> Object.getOwnPropertyDescriptor(url, querySymbol)

{ value: URLSearchParams { 'a' => '1' },
  writable: true,
  enumerable: true,
  configurable: true }

[iambalaam]

Since raising this PR, I have questioned if both parts of the solution are needed (nativeURL and cloned property descriptor/names). I have now tested and know that cloning the property descriptor/names is enough on its own.

I am now unsure if there are any merits of adding the nativeURL, or if I should remove that part?