lib: rename lib/internal/readline.js

This commit moves lib/internal/readline.js to
lib/internal/readline/utils.js. This is in preparation of
adding a readline.promises implementation.

PR-URL: https://github.com/nodejs/node/pull/28753


Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Anto Aravinth <anto.aravinth.cse@gmail.com>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>
Reviewed-By: Shingo Inoue <leko.noor@gmail.com>