lib: remove return values from validation functions

This makes sure the validation functions do not cause any side
effects. Validation functions should ideally only validate the input
without any other effect. Since the input value must be known from
the callee, there is no reason to return the input value.

PR-URL: https://github.com/nodejs/node/pull/26809


Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>