add 2 CMake build options of Dawn (#23096)
### Description
This change adds the following CMake build options for Dawn:
- onnxruntime_BUILD_DAWN_MONOLITHIC_LIBRARY
- OFF by default
- when enabled, builds Dawn as a monolithic library (webgpu_dawn.dll)
- onnxruntime_ENABLE_DAWN_BACKEND_VULKAN
- OFF by default
- when enabled, build with Vulkan backend for Dawn on Windows
- onnxruntime_ENABLE_DAWN_BACKEND_D3D12
- ON by default
- when enabled, build with DirectX 12 backend for Dawn on Windows
### File Size Comparison (Windows)
| Build | cmdline | File Size |
|---|---|---|
| Baseline | --config Release<br/> --build_shared_lib | `12,755,456
onnxruntime.dll` |
| WebGPU D3D12 (default) | --use_webgpu<br/> --config Release<br/>
--build_shared_lib | `17,082,368 dxcompiler.dll`<br/>` 1,508,472
dxil.dll`<br/>`18,708,480 onnxruntime.dll` |
| WebGPU D3D12+Vulkan | --use_webgpu<br/> --config Release<br/>
--build_shared_lib<br/> --cmake_extra_defines<br/>
onnxruntime_ENABLE_DAWN_BACKEND_D3D12=1<br/>
onnxruntime_ENABLE_DAWN_BACKEND_VULKAN=1 | `17,081,344
dxcompiler.dll`<br/>` 1,508,472 dxil.dll`<br/>`19,388,416
onnxruntime.dll` |
| WebGPU Vulkan | --use_webgpu<br/> --config Release<br/>
--build_shared_lib<br/> --cmake_extra_defines<br/>
onnxruntime_ENABLE_DAWN_BACKEND_D3D12=0<br/>
onnxruntime_ENABLE_DAWN_BACKEND_VULKAN=1 | `17,615,872 onnxruntime.dll`
|
| Monolithic | --use_webgpu<br/> --config Release<br/>
--build_shared_lib<br/> --cmake_extra_defines<br/>
onnxruntime_BUILD_DAWN_MONOLITHIC_LIBRARY=1 | `17,082,368
dxcompiler.dll`<br/>` 1,508,472 dxil.dll`<br/>`13,277,696
onnxruntime.dll`<br/>` 5,616,640 webgpu_dawn.dll` |
| External Dawn | --use_webgpu<br/> --config Release<br/>
--build_shared_lib<br/> --cmake_extra_defines<br/>
onnxruntime_USE_EXTERNAL_DAWN=1<br/> --skip_tests | `17,081,344
dxcompiler.dll`<br/>` 1,508,472 dxil.dll`<br/>`13,277,184
onnxruntime.dll`
