[QNN EP] Fuse Gelu pattern into a QNN Gelu Node (#26417)

### Description
- ONNX models exported with older Opset version contains Gelu operator
decomposed into multiple operators (Div, Erf, Add, Mul).
- QNN doesn't support Erf operator but supports Gelu operator
- Since QNN doesn't support Erf operator, the graphs contain Gelu
pattern partition between QNN and CPU EPs and degrading the inference
time.



### Motivation and Context
- Identify and fuse the Gelu pattern into a QNN Gelu node improves the
inference time.

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Co-authored-by: Tirupathi Reddy T <[email protected]>

Author: quic-tirupath