Add fusion script for segment anything v2 (#22167)
### Description
* Add MultiHeadAttention fusion for SAM2.
* Add LayerNormalization fusion for NCHW format by inserting Transpose
from NCHW to NHWC before layer normalization, and add another Transpose
after layer norm to convert NHWC back to NCHW. Hopefully, those extra
Transpose nodes will be removed when prefer_nhwc is enabled later.
* Add a condition that the input shall be 3D when fuse SkipLayerNorm.
* Update convert_to_onnx.py to add `--optimize` and `--use_gpu` options
to output optimized onnx model for CPU/CUDA eps.
* Add an option `--dtype fp16|fp32` in convert_to_onnx.py to support
converting optimized model to float16.
* Update the demo to use the optimized onnx models.
### Motivation and Context
To support optimization of SAM2 for CPU/CUDA eps that is exported in
https://github.com/microsoft/onnxruntime/pull/22119
