Fix corner-case accounting bug in new codeheap allocation (dotnet#107492)

The size of internal CodeHeap structures was not included in
codeheap memory reservation. It caused false OOM exception to
be thrown when JITed method code size was near 64kB multiple

Author: jkotas

src/coreclr/vm/codeman.cpp

@@ -2376,6 +2376,16 @@ HeapList* LoaderCodeHeap::CreateCodeHeap(CodeHeapRequestInfo *pInfo, LoaderHeap
     }
     else
     {
+        // Include internal CodeHeap structures in the reserve
+        allocationSize = ALIGN_UP(allocationSize, VIRTUAL_ALLOC_RESERVE_GRANULARITY);
+        reserveSize = max(reserveSize, allocationSize);
+
+        if (reserveSize != (DWORD) reserveSize)
+        {
+            _ASSERTE(!"reserveSize does not fit in a DWORD");
+            EEPOLICY_HANDLE_FATAL_ERROR(COR_E_EXECUTIONENGINE);
+        }
+
         if (loAddr != NULL || hiAddr != NULL)
         {
 #ifdef _DEBUG