lib: replace charCodeAt with fixed Unicode

PR-URL: https://github.com/nodejs/node/pull/32758


Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>
Reviewed-By: Zeyu Yang <himself65@outlook.com>