Move top-level error properties into an .options and .response property

[szmarczak]

This PR just simplifies error properties. As for now you can access error options in two ways:

1. error.hostname
2. error.gotOptions.hostname

They return the same value. So I removed Object.assign(this, options); and renamed gotOptions to options. So you need to do just error.options.hostname.

Same with the response property. Instead of error.statusCode you need to do error.response.statusCode.

Checklist

• I have read the documentation.
• I have included a pull request description of my changes.
• I have included some tests.
• If it's a new feature, I have included documentation updates.
• Fixed Issue with adding the request/response body to errors #754