`safe_VkPipelineCacheCreateInfo` does not copy its pInitialData from `in_struct`

The current codegen for `vku::safe_VkPipelineCacheCreateInfo` does not copy its souce contents, only the source pointer.

```c++
void safe_VkPipelineCacheCreateInfo::initialize(const VkPipelineCacheCreateInfo* in_struct,
[[maybe_unused]] PNextCopyState* copy_state) {
FreePnextChain(pNext);
sType = in_struct->sType;
flags = in_struct->flags;
initialDataSize = in_struct->initialDataSize;
pInitialData = in_struct->pInitialData;
pNext = SafePnextCopy(in_struct->pNext, copy_state);
}
```

Search for safe_VkPipelineCacheCreateInfo::initialize and the codegen that produces it; compare how pInitialData is handled with other pointer fields. The issue is done when the initializer copies the pointed-to initial data rather than retaining only the source pointer, with existing relevant tests or generated output confirming the behavior.

Written by the indexing model from the issue text.