Packets take SerializeBuffer via move

The existing implemented behavior is that of a transfer of ownership, however
it does it without move semantics.

This doesn't change the behavior but makes it explicitly clear that there
is a transfer of ownership via enforced move semantics.

Also includes some cleanup in the packet classes, including converting the
size parameter to size_t. While no packet will ever be large enough to require
64-bits of size, many places that are initializing packets are doing so
with a size_t parameter, so this will address those warnings here.

common/patches/uf.cpp

@@ -2711,7 +2711,7 @@ namespace UF
 
 		buf.WriteString(new_message);
 
-		auto outapp = new EQApplicationPacket(OP_SpecialMesg, buf);
+		auto outapp = new EQApplicationPacket(OP_SpecialMesg, std::move(buf));
 
 		dest->FastQueuePacket(&outapp, ack_req);
 		delete in;