Pull request: 3998 Make hosts rules match exactly

Merge in DNS/adguard-home from 3998-fix-hosts-gen to master

Closes #3998

Squashed commit of the following:

commit b565d51afb6c292dd16accd45b7d37ed386714e8
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Thu Dec 23 16:25:02 2021 +0300

    aghnet: make hosts rules match exactly

internal/aghnet/hostscontainer_test.go

@@ -346,6 +346,24 @@ func TestHostsContainer(t *testing.T) {
 		testTail: func(t *testing.T, res *urlfilter.DNSResult) {
 			assert.Equal(t, "hello", nRewrites(t, res, 1)[0].NewCNAME)
 		},
+	}, {
+		name: "hello_subdomain",
+		req: urlfilter.DNSRequest{
+			Hostname: "say.hello",
+			DNSType:  dns.TypeA,
+		},
+		testTail: func(t *testing.T, res *urlfilter.DNSResult) {
+			assert.Empty(t, res.DNSRewrites())
+		},
+	}, {
+		name: "hello_alias_subdomain",
+		req: urlfilter.DNSRequest{
+			Hostname: "say.hello.world",
+			DNSType:  dns.TypeA,
+		},
+		testTail: func(t *testing.T, res *urlfilter.DNSResult) {
+			assert.Empty(t, res.DNSRewrites())
+		},
 	}, {
 		name: "lots_of_aliases",
 		req: urlfilter.DNSRequest{