Add dummy placeholder Resolver (implement the null object pattern)

[clue]

This library should include a dummy Resolver that fulfills the current interface without actually resolving any domain names. All calls to resolve() should be handled with a rejected Promise. This class will be useful for components that currently require a Resolver but (potentially) could also work without actually resolving any domain names (reactphp/socket-client, reactphp/socket, reactphp/datagram etc.).

The Resolver is currently a single class with no explicit interface definition, so adding a dedicated NullResolver interface would be a bit of work (and possibly a BC break). Instead, we may want to look into passing a (new) NullExecutor to the current Resolver.

Opening this ticket as a reminder and for referencing related tickets.

[clue]

Afaict this is only really used in the Socket component, so I don't think it's worth the effort.

There are currently no immediate plans to build this from my end (no demand at the moment), but I suppose we would be happy to accept PRs if anybody sees a need for this feature 👍

I'm closing this for now, please feel free to come back with more details if this persists and we can reopen this 👍