lib: switch to Number.isNaN

Number.isNaN is now as fast as `val !== val`. Switch to the more
readable version. Also switch all `isNaN` to `Number.isNaN`.

PR-URL: https://github.com/nodejs/node/pull/18744


Reviewed-By: Weijia Wang <starkwang@126.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Yuta Hiroto <hello@about-hiroppy.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>