Pull request: all: support more $dnsrewrite rr types

Merge in DNS/adguard-home from 2102-dnsrewrite-2 to master

Updates #2102.
Updates #2452.

Squashed commit of the following:

commit b41e57731b4f276e97202e172fa400067174653d
Author: Ainar Garipov <A.Garipov@AdGuard.COM>
Date:   Tue Dec 22 20:40:56 2020 +0300

    dnsforward: improve naming

commit 70b832ce969d8cdcf4224d221e5e1e2057fba6ee
Author: Ainar Garipov <A.Garipov@AdGuard.COM>
Date:   Tue Dec 22 19:36:21 2020 +0300

    all: support more $dnsrewrite rr types

staticcheck.conf

@@ -7,8 +7,11 @@ initialisms = [
 , "DOQ"
 , "DOT"
 , "EDNS"
+, "MX"
+, "PTR"
 , "QUIC"
 , "SDNS"
+, "SVCB"
 ]
 dot_import_whitelist = []
 http_status_code_whitelist = []