[3.12] gh-112169: Documented getaddrinfo/getnameinfo default loop executor usage and implications. (GH-112191) (#120936)

gh-112169: Documented getaddrinfo/getnameinfo default loop executor usage and implications. (GH-112191)
(cherry picked from commit fc297b4ba4c61febeb2d8f5d718f2955c6bbea0a)

Co-authored-by: Alek Kowalczyk <alek.kowalczyk@gmail.com>
Co-authored-by: Guido van Rossum <gvanrossum@gmail.com>
Co-authored-by: Kumar Aditya <kumaraditya@python.org>
Co-authored-by: Carol Willing <carolcode@willingconsulting.com>