Merge in DNS/dnsproxy from 5117-backport-dns64 to master

Updates AdguardTeam/AdGuardHome#5117.

Squashed commit of the following:

commit 7fcd7d84
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Fri Feb 3 15:03:17 2023 +0300

    proxy: fix test

commit ec1b3d76
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Fri Feb 3 14:00:42 2023 +0300

    proxy: imp docs

commit eb0b1e3d
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Thu Feb 2 20:08:40 2023 +0300

    proxy: imp and test

commit d4b9133c
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Thu Feb 2 17:40:56 2023 +0300

    proxy: fix race in test

commit ef90bd32
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Thu Feb 2 15:33:04 2023 +0300

    proxy: fit gocyclo into 10, imp logs

commit 0e25eb68
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Thu Feb 2 14:01:12 2023 +0300

    all: imp code, tests

commit a58f2f2a
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Wed Feb 1 14:35:30 2023 +0300

    proxy: fix const name

commit 266095a9
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Wed Feb 1 14:31:11 2023 +0300

    proxy: rm unused, exp const

commit ccafca50
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Wed Feb 1 13:41:19 2023 +0300

    proxy: backport dns64, depr old api