Add hints to migrate away from async hooks.
Change docs at various places to be more clear that resources are
internals and may change at any time.
PR-URL: https://github.com/nodejs/node/pull/45369
Refs: https://github.com/nodejs/node/pull/45335
Reviewed-By: Geoffrey Booth <webadmin@geoffreybooth.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Stephen Belanger <admin@stephenbelanger.com>
Reviewed-By: Chengzhong Wu <legendecas@gmail.com>
