add bf16 in fp32 out fast path for embedingbag in caffe2 perfkernel (#89198)
Add BF16 in FP32 out kernel into Caffe2 emb perfkernels. And also update the python code-gen files to generate the kernel.
The ut will be covered in the next PR(#89199) in this stack ( Tested by nn.EmbeddingBag with BF16 data type)
Pull Request resolved: https://github.com/pytorch/pytorch/pull/89198
Approved by: https://github.com/jgong5, https://github.com/kit1980
