ZoneLoading: Simulate the vanilla edge case that the chunk size is in the end of the loadbuffer and cannot quite fit into it so the space is padded and the chunk size is loaded from the beginning of the buffer

src/ZoneLoading/Loading/ILoadingStream.h

@@ -1,9 +1,12 @@
 #pragma once
 
+#include <cstdint>
+
 class ILoadingStream
 {
 public:
     virtual ~ILoadingStream() = default;
 
     virtual size_t Load(void* buffer, size_t length) = 0;
+    virtual int64_t Pos() = 0;
 };