http2: support generic `Duplex` streams

Support generic `Duplex` streams through using `StreamWrap`
on the server and client sides, and adding a `createConnection`
method option similar to what the HTTP/1 API provides.

Since HTTP2 is, as a protocol, independent of its underlying transport
layer, Node.js should not enforce any restrictions on what streams
its internals may use.

Ref: https://github.com/nodejs/node/issues/16256
PR-URL: https://github.com/nodejs/node/pull/16269


Reviewed-By: Anatoli Papirovski <apapirovski@mac.com>
Reviewed-By: James M Snell <jasnell@gmail.com>