Expose error.details as a property on ArcGISRequestError and subclasses

[patrickarlt]

Describe the problem

Currently if I wanted to get the details from an error (if they are present). I need to use error.response.details which isn't terribly intuitive.

Describe the proposed solution

Expose a new error.details property on ArcGISRequestError to expose the error.details property in the error response.

Alternatives considered

N/A

Additional Information

Highly relevant to upcoming Places service which puts a lot of information in error.details.