Updates #4865. Squashed commit of the following: commit b874088ee72dfd0cae5f4102fac87e1f26245ddf Author: Ainar Garipov <A.Garipov@AdGuard.COM> Date: Fri Sep 2 14:01:52 2022 +0300 dnsforward: imp code, docs commit a1b95fda58b777a54e7dcd57f0c419200f8fdc15 Author: Ainar Garipov <A.Garipov@AdGuard.COM> Date: Thu Sep 1 19:37:45 2022 +0300 all: refactor dns handler; opt