Revert "net: remove usage of require('util')"

This reverts commit e112fb4c. This commit broke parallel/test-net-access-byteswritten.

Refs: https://github.com/nodejs/node/pull/26807#issuecomment-476016632

Did a bisect and arrived at the same conclusion.

Collaborators, please 👍 here to fast-track.

Checklist

• make -j4 test (UNIX), or vcbuild test (Windows) passes
• commit message follows commit guidelines