util: add util.sleep()

The first commit is the libuv 1.34.0 upgrade (https://github.com/nodejs/node/pull/30783).

The second commit adds a util.sleep() function.

Checklist

• make -j4 test (UNIX), or vcbuild test (Windows) passes
• tests and/or benchmarks are included
• documentation is changed or added
• commit message follows commit guidelines