DefaultHandlerExceptionResolver supports ErrorResponse

DefaultHandlerExceptionResolver now supports ErrorResponse exceptions
and can map them to HTTP status and headers of the response. This
includes not only exceptions from spring-web,  but also any other
exception that implements ErrorResponse.

ResponseEntityExceptionHandler is updated along the same lines, now
also handling any ErrorResponseException. It can be used it for
RFC 7807 support for Spring MVC's own exceptions.

See gh-27052

Author: rstoyanchev