Re-export error code constants from `dns/promises`

[leftshift]

What is the problem this feature will solve?

When writing code that uses the promise based dns library, it's quite convenient to just import dns/promises.

However, when checking for the type of error with err.code, it's nicer and more robust to do a comparisons with the error code constants instead of doing a string comparison:

try {
  res = await dns.resolve4([...])
} catch(e) {
  if (e.code == dns.NOTFOUND) { // instead of e.code == 'ENOTFOUND'
    [...]
  }
}

However, unfortunately, NOTFOUND and friends are only exported from the dns module, not from dns/promises.

What is the feature you are proposing to solve the problem?

Re-Export all dns error code constants from dns/promises.

What alternatives have you considered?

Alternatively, code needs to either import dns and dns/promises under different names (which might be a bit confusing), or just import dns and use the promise based api through dns.promises (seems needlessly verbose).

[aduh95]

The same applies to node:fs, currently my goto way is to

import { promises as fs, constants as fsConstants } from 'node:fs'
import { promises as dns, constants as dnsConstants } from 'node:dns'

Would you like to send a PR to address that?