Large code size caused by vtable initialization in `prepareVTables` function

[learnforpractice]

The generated vtable initialization code in the prepareVTables function is quite significant and result in increased code size and increased initialization time.

By performing a simple test, the value of classRealizationCnt can be increased to 1487, resulting in a significant increase in the time required for vtable initialization and leading to a considerable increase in code size.

Moreover, the vtable initialization code could prevent the optimization of some thunk functions that are not being used, further exacerbating the issue.