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/upgrade.go

@@ -11,9 +11,9 @@ import (
 	"strings"
 	"time"
 
-	"github.com/AdguardTeam/AdGuardHome/internal/aghnet"
 	"github.com/AdguardTeam/golibs/errors"
 	"github.com/AdguardTeam/golibs/log"
+	"github.com/AdguardTeam/golibs/netutil"
 	"github.com/google/renameio/maybe"
 	"golang.org/x/crypto/bcrypt"
 	yaml "gopkg.in/yaml.v2"
@@ -545,7 +545,7 @@ func addQUICPort(ups string, port int) (withPort string) {
 	}
 
 	var host string
-	host, err = aghnet.SplitHost(upsURL.Host)
+	host, err = netutil.SplitHost(upsURL.Host)
 	if err != nil || host != upsURL.Host {
 		return ups
 	}