Pull request: dhcpd: add ips and text option types

Updates #2385.

Squashed commit of the following:

commit ce8467f1c013c6b3fef59667084e2c6569a7213c
Author: Ainar Garipov <A.Garipov@AdGuard.COM>
Date:   Mon Mar 15 19:02:17 2021 +0300

    dhcpd: add ips and text option types

internal/dhcpd/server.go

@@ -96,5 +96,5 @@ type V6ServerConf struct {
 
 type dhcpOption struct {
 	code uint8
-	val  []byte
+	data []byte
 }