Match CNAME records against the blocklists

[ameshkov]

Check out the original issue:
uBlockOrigin/uBlock-issues#780

Here's what we should do:

1. Match CNAME records against the blocklists
2. Indicate in the query log that the response was blocked by matching a CNAME. It'd be ideal if we print the original response there as well.
3. Please note, that if there's an exception rule matching the DNS query's question, you should not check the CNAME.

Additionally to implementing this in AdGuard Home, we should do the following:

1. Update the dnsproxy's mobile API
2. Update AdGuard DNS to do this as well
3. File a feature request to github.com/AdguardTeam/DnsLibs

[hoshsadiq]

Just in case the following is overlooked.. It would be good if this goes through the whole CNAME chain. I.e.

ad.firstparty.com cname unblocked.company2.com
unblocked.company2.com cname blocked.adcompany.com
blocked.adcompany.com

This request should be blocked if either unblocked.company2.com or blocked.adcompany.com is blocked.

[ameshkov]

@hoshsadiq all CNAME records in the chain will be present in the recursor's response so this is not a problem:

$ nslookup test2.meshkov.info
Server:		2001:db8:7c02:1::1
Address:	2001:db8:7c02:1::1#53

Non-authoritative answer:
test2.meshkov.info	canonical name = test1.meshkov.info.
test1.meshkov.info	canonical name = example.org.
Name:	example.org
Address: 93.184.216.34

[hoshsadiq]

Aah! Perfect!