dgram: convert to using internal/errors

Covert lib/dgram.js over to using lib/internal/errors.js
for generating Errors. See
[using-internal-errors.md](https://github.com/nodejs/node/blob/master/doc/guides/using-internal-errors.md)
for more details.

I have not addressed the cases that use errnoException() and
exceptionWithHostPort() helper methods as changing these would require
fixing the tests across all of the different files that use them. In
addition, these helpers already add a `code` to the Error and we'll
have to discuss how that interacts with the `code` used by
lib/internal/errors.js.  I believe we should convert all users
of errnoException and exceptionWithHostPort in a PR dedicated to
that conversion.

PR-URL: https://github.com/nodejs/node/pull/12926
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Franziska Hinkelmann <franziska.hinkelmann@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben.bridgewater@fintura.de>

doc/api/errors.md

@@ -703,6 +703,35 @@ in some cases may accept `func(undefined)` but not `func()`). In most native
 Node.js APIs, `func(undefined)` and `func()` are treated identically, and the
 [`ERR_INVALID_ARG_TYPE`][] error code may be used instead.
 
+<a id="ERR_SOCKET_ALREADY_BOUND"></a>
+### ERR_SOCKET_ALREADY_BOUND
+An error using the `'ERR_SOCKET_ALREADY_BOUND'` code is thrown when an attempt
+is made to bind a socket that has already been bound.
+
+<a id="ERR_SOCKET_BAD_PORT"></a>
+### ERR_SOCKET_BAD_PORT
+
+An error using the `'ERR_SOCKET_BAD_PORT'` code is thrown when an API
+function expecting a port > 0 and < 65536 receives an invalid value.
+
+<a id="ERR_SOCKET_BAD_TYPE"></a>
+### ERR_SOCKET_BAD_TYPE
+
+An error using the `'ERR_SOCKET_BAD_TYPE'` code is thrown when an API
+function expecting a socket type (`udp4` or `udp6`) receives an invalid value.
+
+<a id="ERR_SOCKET_CANNOT_SEND"></a>
+### ERR_SOCKET_CANNOT_SEND
+
+An error using the `'ERR_SOCKET_CANNOT_SEND'` code is thrown when data
+cannot be sent on a socket.
+
+<a id="ERR_SOCKET_DGRAM_NOT_RUNNING"></a>
+### ERR_SOCKET_DGRAM_NOT_RUNNING
+
+An error using the `'ERR_SOCKET_DGRAM_NOT_RUNNING'` code is thrown
+when a call is made and the UDP subsystem is not running.
+
 <a id="ERR_STDERR_CLOSE"></a>
 ### ERR_STDERR_CLOSE