Retry with different resolvers

[pdelteil]

Please describe your feature request:

Often times while scanning domains you will get many false positives or REFUSED states. It would be useful to define a retry flag that retries with N resolvers. I'm assuming the current retry flag uses the same resolver every time.

Describe the use case of this feature:

Let's say we are looking for resolving domains (NOERROR status code), due to resolvers being blocked or malfunctioning (or rate limited?) the result might be REFUSED. I would like then to have this conditions matched:

• Only give NOERROR if at least 1 resolver gave NOERROR.
• Give REFUSED if N resolvers gave REFUSED. This means dnsx choosing N different resolvers from the -r parameter.
• Give SERVFAIL if N resolvers gave SERVFAIL.

Show a warning if N is greater than the resolvers defined in the -r parameter.

Thank you.