child_process: name anonymous functions

Refs: https://github.com/nodejs/node/issues/8913

PR-URL: https://github.com/nodejs/node/pull/20399


Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>