[js/web] update the build script for webgpu to enable model dump by default (#19707)
### Description
update the build script for webgpu to enable model dump by default
Now if using build_jsep.bat to build debug, the model dump is enabled.
Using
[`optimizedModelFilePath`](https://onnxruntime.ai/docs/api/js/interfaces/InferenceSession.SessionOptions.html#optimizedModelFilePath)
in session option can dump the optimized model in browser
### Motivation and Context
Helps to debug/rule out problems may related to model optimizer.