Pull request: all: mv some utilities to netutil

Merge in DNS/adguard-home from mv-netutil to master

Squashed commit of the following:

commit 5698fceed656dca7f8644e7dbd7e1a7fc57a68ce
Author: Ainar Garipov <A.Garipov@AdGuard.COM>
Date:   Mon Aug 9 15:44:17 2021 +0300

    dnsforward: add todos

commit 122fb6e3de658b296931e0f608cf24ef85547666
Author: Ainar Garipov <A.Garipov@AdGuard.COM>
Date:   Mon Aug 9 14:27:46 2021 +0300

    all: mv some utilities to netutil

internal/home/controlinstall.go

@@ -16,6 +16,7 @@ import (
 
 	"github.com/AdguardTeam/AdGuardHome/internal/aghnet"
 	"github.com/AdguardTeam/golibs/log"
+	"github.com/AdguardTeam/golibs/netutil"
 )
 
 // getAddrsResponse is the response for /install/get_addresses endpoint.
@@ -311,7 +312,7 @@ func (web *Web) handleInstallConfigure(w http.ResponseWriter, r *http.Request) {
 				w,
 				http.StatusBadRequest,
 				"can not listen on IP:port %s: %s",
-				aghnet.JoinHostPort(req.Web.IP.String(), req.Web.Port),
+				netutil.JoinHostPort(req.Web.IP.String(), req.Web.Port),
 				err,
 			)