test: refactor and simplify test-repl-preview

Use an object to indicate which part belongs to the input and which
to the output.
On top of that this also simplifies the expected output by
automatically inserting the default repl line for previews and by
automatically checking for the correct output line length.

PR-URL: https://github.com/nodejs/node/pull/32154


Reviewed-By: Shelley Vohr <codebytere@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>