"Deno.upgradeHttp" API needs to be rewritten for Node compat

[bartlomieju]

Required for denoland/std#2061

Node emits "upgrade" event with "request", "socket" and "head" arguments, when a request is received that has Connection: upgrade header. Deno.upgradeHttp was meant to be a solution to polyfill that Node API, however the semantics of this API are strictly related to how upgrades work in hyper. Deno.upgradeHttp resolves a promise only after a response is sent back (again, mandated by hyper), but in case of Node's API it is callers responsibility in write the response manually.

Because of that we are unable to polyfill Node's server API which is a (most likely) the last blocker for Vite compatibility denoland/std#2055 We need to change Deno.upgradeHttp in such a way that it will verify that passed request is actually an upgrade request and yield the request back, along with the underlying connection and first packet of data (could be empty).

CC @littledivy

[bartlomieju]

This was already addressed in new Deno.serve() API.