FEXCore: Fixes ever shrinking JIT code buffer

I accidentally replaced a couple usages of `AllocatedSize` with
`GetAllocatedSize()`. This resulted in a JIT buffer that ran out of
space would actually allocate a slightly smaller buffer each time, and
then it cascades downwards resulting in catastrophic performance.

Fix the use in `SharedCodeBufferManager.cpp` and `Core.cpp` which were
incorrect and renames the function to be more explicit.

FEXCore/Source/Interface/Core/SharedCodeBufferManager.cpp

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