lib: remove internal `util._extends()` usage

This removes all internal calls to the deprecated `_extends()`
function. It is slower than `Object.assign()` and the object spread
notation since V8 6.8 and using the spread notation often also
results in shorter code.

PR-URL: https://github.com/nodejs/node/pull/25105


Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>