[webgpu] Use workgroup memory to reduce register pressure

[Jiajia Qin (qjia7)]

On Qualcomm Adreno X1 GPUs, the previous implementation of the FlashAttentionProgram shader in the WebGPU backend was causing high register pressure, leading to performance degradation. This PR uses workgroup memory to reduce the register pressure and improve performance.

TTFT for phi4 with 1K inputs becomes 10s from 40s on Qualcomm Adreno X1 GPU.

[Sushanth Rajasankar (sushraja-msft)]

LGTM thanks

[Jiajia Qin (qjia7)]

Guenther Schmuelling (@guschmue) Need your help on full perf test to ensure it won't bring regressions on other GPUs. Thanks.

[Guenther Schmuelling (guschmue)]

/azp run Linux QNN CI Pipeline,Win_TRT_Minimal_CUDA_Test_CI,Windows ARM64 QNN CI Pipeline,Windows GPU Doc Gen CI Pipeline,Windows x64 QNN CI Pipeline,web_Debug / build_onnxruntime_web,web_Release / build_onnxruntime_web

[azure-pipelines]

Azure Pipelines successfully started running 5 pipeline(s).

[Guenther Schmuelling (guschmue)]

azp /run web_Debug / build_onnxruntime_web,web_Release / build_onnxruntime_web,webgpu_build_x64_RelWithDebInfo, webgpu_external_dawn_build_x64_RelWithDebInfo,webgpu_minimal_build_edge_build_x64_RelWithDebInfo,Win_TRT_Minimal_CUDA_Test_CI,Windows ARM64, QNN CI Pipeline,Windows GPU CUDA CI Pipeline,Windows GPU DML CI Pipeline,Windows GPU Doc Gen CI Pipeline,Windows GPU TensorRT CI Pipeline,
Windows OpenVINO CI Pipeline

[Guenther Schmuelling (guschmue)]

/azp run Windows OpenVINO CI Pipeline

[azure-pipelines]

No pipelines are associated with this pull request.

[Guenther Schmuelling (guschmue)]

/azp run web_Debug / build_onnxruntime_web,web_Release / build_onnxruntime_web,webgpu_build_x64_RelWithDebInfo, webgpu_external_dawn_build_x64_RelWithDebInfo,webgpu_minimal_build_edge_build_x64_RelWithDebInfo,Win_TRT_Minimal_CUDA_Test_CI,Windows ARM64, QNN CI Pipeline,Windows GPU CUDA CI Pipeline,Windows GPU DML CI Pipeline,Windows GPU Doc Gen CI Pipeline,Windows GPU TensorRT CI Pipeline

[azure-pipelines]

Azure Pipelines successfully started running 2 pipeline(s).

[Guenther Schmuelling (guschmue)]

/azp run build_x64_release

[azure-pipelines]

No pipelines are associated with this pull request.

[Guenther Schmuelling (guschmue)]

sorry, needs to be merged with main

[Guenther Schmuelling (guschmue)]

emscripten build complains about:

onnxruntime/onnxruntime/contrib_ops/webgpu/bert/flash_attention.cc:934:72: error: '&&' within '||' [-Werror,-Wlogical-op-parentheses]
  934 |          (context.AdapterInfo().vendor == std::string_view{"qualcomm"} && parameters.head_size_ % 8 == 0 || parameters.head_size_ % 4 == 0);
      |           ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~
/mnt/vss/_work/onnxruntime/onnxruntime/onnxruntime/contrib_ops/webgpu/bert/flash_attention.cc:934:72: note: place parentheses around the '&&' expression to silence this warning
  934 |          (context.AdapterInfo().vendor == std::string_view{"qualcomm"} && parameters.head_size_ % 8 == 0 || parameters.head_size_ % 4 == 0);
      |                                                                        ^
      |           (