LookupServer: Store DNSName's in HashMap's directly

DNSName can now take care of case conversion when comparing using traits.
It still intentionally doesn't implement operator ==; you have to explicitly
decide whether you want case-sensitive or case-insensitive comparison.

This change makes caches (and /etc/hosts) case-transparent: we will now match
domains if they're the same except for the case.

Userland/Services/LookupServer/DNSName.h

@@ -43,6 +43,12 @@ public:
 
     void randomize_case();
 
+    class Traits : public AK::Traits<DNSName> {
+    public:
+        static unsigned hash(const DNSName& name);
+        static bool equals(const DNSName&, const DNSName&);
+    };
+
 private:
     String m_name;
 };