test: increase coverage for util.inspect()

Confirm that own constructor value displays correctly.

Refs: https://coverage.nodejs.org/coverage-0d468ab200584c3a/lib/internal/util/inspect.js.html#L550

PR-URL: https://github.com/nodejs/node/pull/36228


Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: Juan José Arboleda <soyjuanarbol@gmail.com>
Reviewed-By: Michael Dawson <midawson@redhat.com>
Reviewed-By: James M Snell <jasnell@gmail.com>