Add ability to force close persistent connections

[jsumners]

What is the problem this feature will solve?

As noted in https://nodejs.org/dist/latest-v16.x/docs/api/net.html#serverclosecallback, a net.Server will not fully close until all persistent (keep-alive) connections have reached the end of their timeout. In other languages/frameworks, e.g. Java, C#, or PHP, this is not a problem because applications written with them are typically hosted within a dedicated HTTP server that will deal with this on the application's behalf. However, if we look at another language in which applications are typically written to provide a direct HTTP server we can see that this problem showed up there and has been solved -- golang/go#4674 (comment) (final resolution https://go.dev/doc/go1.8#http_shutdown):

HTTP Server Graceful Shutdown
The HTTP Server now has support for graceful shutdown using the new Server.Shutdown method and abrupt shutdown using the new Server.Close method.

https://pkg.go.dev/net/http#Server.Close

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

I propose that Node.js internally track persistent connections and provide a method to forcefully close them.

What alternatives have you considered?

We have implemented a, what I would call hacky, solution for this in Fastify -- fastify/fastify#3619

The hope is that if Node.js internalizes it, it can be more performant.

[jsumners]

cc: @mcollina

[mcollina]

cc @nodejs/http