test: refactor `test-readline-interface` to be shorter

PR-URL: https://github.com/nodejs/node/pull/38691


Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Darshan Sen <raisinten@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>