[webgpu] optimize emscripten inter-op for buffer

[fs-eire]

Description

optimize emscripten inter-op for buffer.

There are huge amount of calls to WebGPU API wgpuBufferGetSize and wgpuBufferGetUsage. The original implementation was using inter-op (JavaScript implementation). This change modifies the implementation to use C++ code so that inter-op is avoid.

In order to achieve this, I need to add 2 fields mSize and mUsage into WGPUBufferImpl class and value of those fields are set in constructor. This should be safe considering those 2 properties of a buffer is immutable.

Motivation and Context

Improve E2E perf

[Copilot]

Pull Request Overview

This PR adds a performance optimization patch for Emscripten-based WebGPU interop by caching buffer size and usage fields in the C++ WGPUBufferImpl class to avoid frequent JavaScript-to-C++ boundary crossings.

Key Changes:

• Adds new patch file emscripten_interop_opt.patch that caches buffer size and usage as fields in WGPUBufferImpl
• Removes JavaScript functions wgpuBufferGetSize and wgpuBufferGetUsage that previously crossed the JS/C++ boundary
• Updates the Dawn patch command in CMake to apply the new optimization patch

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

File	Description
cmake/patches/dawn/emscripten_interop_opt.patch	New patch file that modifies Dawn's Emscripten WebGPU implementation to cache buffer metadata in C++
cmake/external/onnxruntime_external_deps.cmake	Adds application of the new optimization patch to the Dawn build process

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