test: increase test coverage for fs.promises read

PR-URL: https://github.com/nodejs/node/pull/22800


Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Ben Coe <bencoe@gmail.com>
Reviewed-By: Yuta Hiroto <hello@hiroppy.me>
Reviewed-By: Michael Dawson <michael_dawson@ca.ibm.com>