Support net.BlockList in http.Agent options

[satire-foxfire]

What is the problem this feature will solve?

Enable users to allow or block requests when using http.request, fetch, etc.

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

Node.js already supports net.BlockList, it'd be awesome if you could simply pass in an instance of net.BlockList when creating a custom http.Agent and then have it automatically enforce the IP checks for you.

What alternatives have you considered?

I believe the only way to do this at the moment is a bit boilerplate-y, which would be using a custom lookup function that calls dns.lookup(hostname) manually, then calls blocklist.check(address) manually, and then if it flags, throw an error, else return the address.

Although that still isn't a complete solution because the lookup function isn't called for hostnames that are already IP addresses, so even more code to do the check fully :(