[node-compat] process.stdin.unref should warn instead of throwing unreachable

[brc-dd]

Example code:

import process from 'node:process'
import readline from 'node:readline'

const input = readline.createInterface({
  input: process.stdin
})

process.stdin.unref()

In node, this immediately exits the process. In deno, it throws:

error: Uncaught (in promise) NodeCompatAssertionError: unreachable
    at unreachable (ext:deno_node/_util/asserts.ts:16:9)
    at TTY.unref (ext:deno_node/internal_binding/handle_wrap.ts:41:5)
    at ReadStream.unref (node:net:643:20)

I believe this is currently not supported, but it should just warnNotImplemented instead of throwing?

Corresponding Node docs - https://nodejs.org/api/readline.html#readlinecreateinterfaceoptions (Also here in polyfill comments:)

deno/ext/node/polyfills/_readline.d.ts

Lines 350 to 358 in aadcd64

	* When creating a `readline.Interface` using `stdin` as input, the program
	* will not terminate until it receives `EOF` (Ctrl+D on
	* Linux/macOS, Ctrl+Z followed by Return on
	* Windows).
	* If you want your application to exit without waiting for user input, you can `unref()` the standard input stream:
	*
	* ```js
	* process.stdin.unref();
	* ```

Version:

deno 1.39.1 (release, aarch64-apple-darwin)
v8 12.0.267.8
typescript 5.3.3

[kt3k]

Sounds reasonable to me. Can you send a PR?