SharedCodeBufferManager: Leak less internal details about implementation

The various places that were using the CodeBuffer object were using
internal implementation details that are changing as we move over to a
bitmap allocator.

Preempt this by hiding some of the implementation details early without
changing behaviour. `GetBufferBase` is still technically leaking some of
the internal details, but it needs changes around how relocations are
being handled and how the disk cache validation works in order to handle
that right now.

Should be no functional change.

FEXCore/Source/Interface/Core/SharedCodeBufferManager.cpp

@@ -88,7 +88,7 @@ fextl::shared_ptr<CodeBuffer> SharedCodeBufferManager::StartLargerCodeBuffer() {
     return GetLatest();
   }
 
-  auto NewCodeBufferSize = GetLatest()->AllocatedSize;
+  auto NewCodeBufferSize = GetLatest()->GetAllocatedSize();
   NewCodeBufferSize = std::min<size_t>(NewCodeBufferSize * 2, MAX_CODE_SIZE);
   return AllocateNew(NewCodeBufferSize);
 }