[webgpu] support Pad operator

[xhcao]

Description

Motivation and Context

[xhcao]

@jchen10 @hujiajie PTAL, thanks

[guschmue]

/azp run ONNX Runtime Web CI Pipeline,Windows GPU CI Pipeline,Linux Android Emulator QNN CI Pipeline

[guschmue]

/azp run Linux CPU CI Pipeline,Linux CPU Minimal Build E2E CI Pipeline,Linux GPU CI Pipeline,Linux GPU TensorRT CI Pipeline,Linux OpenVINO CI Pipeline,Linux QNN CI Pipeline,MacOS CI Pipeline,Windows ARM64 QNN CI Pipeline,Windows CPU CI Pipeline

[guschmue]

/azp run Windows GPU TensorRT CI Pipeline,onnxruntime-binary-size-checks-ci-pipeline,orttraining-linux-ci-pipeline,orttraining-linux-gpu-ci-pipeline,orttraining-ortmodule-distributed,Windows x64 QNN CI Pipeline,Big Models

[azure-pipelines]

Azure Pipelines successfully started running 2 pipeline(s).

[guschmue]

/azp run Windows GPU CUDA CI Pipeline,Windows GPU DML CI Pipeline,Windows GPU Doc Gen CI Pipeline

[azure-pipelines]

Azure Pipelines successfully started running 4 pipeline(s).

[azure-pipelines]

Azure Pipelines successfully started running 3 pipeline(s).

[azure-pipelines]

Azure Pipelines successfully started running 9 pipeline(s).

[xhcao]

@fs-eire @guschmue Please help to trigger the bots again. Last version failed on Mac OS, but could compile correctly on Windows. I had changed the code, but not ensured it worked correctly on Mac OS. The compiling error was shown as below.
/Users/runner/work/1/s/onnxruntime/core/providers/webgpu/tensor/pad.h:16:54: error: member initializer 'Program' does not name a non-static data member or base class PadProgram(const Mode mode, bool dim_value_zero) : Program{"Pad"}, mode_{mode}, dim_value_zero_{dim_value_zero} {}

[guschmue]

/azp run ONNX Runtime Web CI Pipeline,Windows GPU CI Pipeline,Linux Android Emulator QNN CI Pipeline

[guschmue]

/azp run Linux CPU CI Pipeline,Linux CPU Minimal Build E2E CI Pipeline,Linux GPU CI Pipeline,Linux GPU TensorRT CI Pipeline,Linux OpenVINO CI Pipeline,Linux QNN CI Pipeline,MacOS CI Pipeline,Windows ARM64 QNN CI Pipeline,Windows CPU CI Pipeline

[guschmue]

/azp run Windows GPU TensorRT CI Pipeline,onnxruntime-binary-size-checks-ci-pipeline,orttraining-linux-ci-pipeline,orttraining-linux-gpu-ci-pipeline,orttraining-ortmodule-distributed,Windows x64 QNN CI Pipeline,Big Models

[azure-pipelines]

Azure Pipelines successfully started running 2 pipeline(s).

[guschmue]

/azp run Windows GPU CUDA CI Pipeline,Windows GPU DML CI Pipeline,Windows GPU Doc Gen CI Pipeline

[azure-pipelines]

Azure Pipelines successfully started running 4 pipeline(s).

[azure-pipelines]

Azure Pipelines successfully started running 3 pipeline(s).

[azure-pipelines]

Azure Pipelines successfully started running 9 pipeline(s).