Attention Operator (CPU) (#25156)
### Description
Implementation Attention(23) for CPU.
The backend tests from onnx were wrong for Attention (see
https://github.com/onnx/onnx/pull/7142). The onnx version needs to be
updated to make all tests pass. The implementation matches the reference
implementation after onnx was fixed.
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Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>
Co-authored-by: Ti-Tai Wang <titaiwang@microsoft.com>
Co-authored-by: kunal-vaishnavi <115581922+kunal-vaishnavi@users.noreply.github.com>
