webgpu : add COUNT_EQUAL support (#31578)
* webgpu : add COUNT_EQUAL support
Assisted-by: Codex
* webgpu : reduce small COUNT_EQUAL inputs in one dispatch
Assisted-by: Codex
* webgpu : simplify COUNT_EQUAL and reuse existing tests
* webgpu : move COUNT_EQUAL pipeline cache declaration
* Update ggml/src/ggml-webgpu/ggml-webgpu.cpp
Co-authored-by: Masashi Yoshimura <yoshimura.masashi.frbs@gmail.com>
* tests : simplify COUNT_EQUAL coverage
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Co-authored-by: Masashi Yoshimura <yoshimura.masashi.frbs@gmail.com>
