PR description
This is a follow-up on #18991 which does 3 things:
- improves privacy of a node listening to multiple addresses via adding cache index by local socket addr (suggested here)
- documents on the choice of 24h cache lifetime
- addresses nits from "Cache responses to GETADDR to prevent topology leaks" #18991
This is a backport of core#19697 [1/4]
https://github.com/bitcoin/bitcoin/pull/19697/commits/42ec5585424ceb91bed07826dde15697c020661a