Remove SetIncludeAllowed(true) from the DNS record zone parser.
The $INCLUDE directive allows opening arbitrary files via os.Open,
which is unnecessary and dangerous when parsing a single record string
from configuration (especially remote profiles).
Fix displayRuleIndex arithmetic in dns/router.go that computed
2*index+1 instead of the correct 0-based index. This was a
reintroduction of a bug previously fixed in be8ee370a. Both
matchDNS and logRuleMatch now use the index directly, matching
the pattern in route/route.go.
The cache lookup was performed before rule matching, using the caller's
strategy (usually AsIS/0) instead of the resolved strategy. This caused
cache misses when ipv4_only was configured globally but the cache lookup
expected both A and AAAA records.
Remove LookupCache and ExchangeCache from Router, as the cache checks
inside client.Lookup and client.Exchange already handle caching correctly
after rule matching with the proper strategy and transport.
