[js/web] update the build script for webgpu to enable model dump by d…

…efault (#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.

js/build_jsep.bat

@@ -17,7 +17,7 @@ set BUILD_DIR=%ROOT%build_jsep
 :arg1
 if ["%~1"]==["d"] (
     set CONFIG=Debug
-    set CONFIG_EXTRA_FLAG=--enable_wasm_debug_info --enable_wasm_profiling
+    set CONFIG_EXTRA_FLAG=--enable_wasm_debug_info --enable_wasm_profiling --cmake_extra_defines onnxruntime_ENABLE_WEBASSEMBLY_OUTPUT_OPTIMIZED_MODEL=1
     goto :arg2
 )
 if ["%~1"]==["r"] (