chore: decrease DomainTrie's memory use

dns/filters.go

@@ -79,6 +79,7 @@ func NewDomainFilter(domains []string) *domainFilter {
 	for _, domain := range domains {
 		_ = df.tree.Insert(domain, struct{}{})
 	}
+	df.tree.FinishInsert()
 	return &df
 }
 

dns/resolver.go

@@ -435,6 +435,7 @@ func NewResolver(config Config) *Resolver {
 		for domain, nameserver := range config.Policy {
 			_ = r.policy.Insert(domain, NewPolicy(transform([]NameServer{nameserver}, defaultResolver)))
 		}
+		r.policy.FinishInsert()
 	}
 
 	fallbackIPFilters := []fallbackIPFilter{}