Fix write-heap-buffer-overflow in copy_out

Summary:
Also add a check on dtypes, make sure out and src dtypes are the same. Otherwise we may copy the wrong dtype without conversion.
---

The crash is a write-heap-buffer-overflow that occurs in the `torch::executor::native::copy_out` function. The root cause is that the `std::memcpy` operation in this function does not check if the destination buffer `out` is large enough to hold the data from the source tensor `src`. Specifically, the condition `internal::sizes_match_ignoring_leading_1s(out.sizes(), src.sizes())` checks if the sizes of `out` and `src` match, ignoring any leading dimensions of size 1 in `out`, but it does not guarantee that `out.nbytes()` is greater than or equal to `src.nbytes()`.

The patch fixes the crash by adding an additional check `out.nbytes() >= src.nbytes()` before performing the `std::memcpy` operation. This ensures that the destination buffer `out` is large enough to hold the data from `src`, preventing the buffer overflow.

```cpp
if (internal::sizes_match_ignoring_leading_1s(out.sizes(), src.sizes()) &&
    src.numel() > 0 && out.nbytes() >= src.nbytes()) {
  std::memcpy(out.mutable_data_ptr(), src.const_data_ptr(), src.nbytes());
}
```

Other considerations that reviewers should take into account when validating the patch include verifying that the additional check does not introduce any performance regressions and that it correctly handles edge cases, such as when `src` is empty or when `out` and `src` have different data types. Reviewers should also check that the patch does not affect the functionality of the `copy_out` function in other scenarios. Additionally, it is worth verifying that the fix is consistent with the existing error handling and checking mechanisms in the `copy_out` function.

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Differential Revision: D80885980

Author: lucylq

kernels/portable/cpu/op_copy.cpp

@@ -49,7 +49,8 @@ Tensor& copy_out(
   // Use direct copy fast path if broadcast is not needed and tensors are
   // non-empty
   if (internal::sizes_match_ignoring_leading_1s(out.sizes(), src.sizes()) &&
-      src.numel() > 0) {
+      src.numel() > 0 && out.nbytes() >= src.nbytes() &&
+      tensors_have_same_dtype(src, out)) {
     std::memcpy(out.mutable_data_ptr(), src.const_data_ptr(), src.nbytes());
   } else {
     ET_SWITCH_REALHBBF16_TYPES(in.scalar_type(), ctx, op_name, CTYPE, [&]() {