onnxruntime

[QAT] Graph transformer to fuse QDQ pattern into FakeQuant (#13777)

To perform QAT in onnxruntime, `FakeQuant` op was introduced in #13649.

The onnxruntime quantization tool generates a post training static
quantization onnx model with `QuantizeLinear`->`DequantizeLinear` nodes.
To perform QAT, this pattern needs to be transformed to `FakeQuant`.

This pull request introduces a graph transformer that looks for the
`Q->DQ` pattern and fuses it to a `FakeQuant` node.