test: increase coverage for readline

1. test call readline.Interface without new should return instance
Refs: https://coverage.nodejs.org/coverage-f7dd330ba0e7bfa9/lib/readline.js.html#L101

2. test keypress ctrl + c should close readline interface
Refs: https://coverage.nodejs.org/coverage-f7dd330ba0e7bfa9/lib/readline.js.html#L891

PR-URL: https://github.com/nodejs/node/pull/36389
Refs: https://coverage.nodejs.org/coverage-f7dd330ba0e7bfa9/lib/readline.js.html#L101
Refs: https://coverage.nodejs.org/coverage-f7dd330ba0e7bfa9/lib/readline.js.html#L891


Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>