[WebGPU] Add int32 support to Relu opset 14 (#33789)
### Description
<!-- Describe your changes. -->
Adds int32 support to the WebGPU EP `Relu` kernel for opset 14+.
- `onnxruntime/core/providers/webgpu/math/unary_elementwise_ops.cc`: the
`Relu` opset 14 kernel now uses the existing `SignedNumberTypes()`
helper (float, float16, int32) instead of `WebGpuSupportedFloatTypes()`.
Opsets 6-12 and 13 stay float-only because ONNX added the integer types
in Relu-14. The shader is unchanged: `select(x_value_t(0), a, a >
x_value_t(0))` is valid WGSL for `vec4<i32>`.
- `onnxruntime/test/providers/webgpu/activation/activation_op_test.cc`:
new `WebGpuActivationTest.Relu_Int32_Opset14_WebGpu`. It runs on the
WebGPU EP only with `kOrtSessionOptionsDisableCPUEPFallback=1`, so a
missing kernel fails the test instead of silently running on CPU (the
CPU EP does register int32 Relu-14). It covers `INT32_MIN`, `-1`, `0`,
`1` and `INT32_MAX` with shape `{7}` (partial trailing vec4) and `{1, 2,
2, 2}` (full vec4s). It skips before constructing `OpTester` when the
WebGPU EP is unavailable.
Out of scope: int8 and int64 Relu, which WGSL does not support natively.
#### Validation
Built with the WebGPU EP from a local, unpushed merge of this commit and
a separate WebGPU Gather commit into `main` (121e34d92b).
- `onnxruntime_provider_test
--gtest_filter="WebGpuActivationTest.*:ActivationOpTest.Relu*:GatherOpTest.*:CastOpTest.*:GatherElementsOpTest.*:GatherNDOpTest.*"`:
**passed**, 268/268 with 0 skipped. This includes
`WebGpuActivationTest.Relu_Int32_Opset14_WebGpu`.
- Negative check: with the Relu-14 registration reverted to
`WebGpuSupportedFloatTypes()`,
`WebGpuActivationTest.Relu_Int32_Opset14_WebGpu` **fails** at session
init with "fallback to CPU EP has been explicitly disabled". This
confirms the test catches a missing WebGPU kernel.
- `lintrunner -a` and clang-format 20.1.8 on the changed files: no
issues.
- WPT `webnn/conformance_tests/relu.https.any.js?gpu`: **16/18 passed**,
up from 15/18 before. "relu int32 4D tensor" now passes. The 2 remaining
failures are the optional int8 and int64 subtests, which are out of
scope. Tested with the WebGPU plugin EP built from `main` 121e34d92b
plus this PR and the Gather int8 PR (local merge `5c68bbb9f9`), Edge
Canary 159.0.4372.0, NVIDIA RTX Spark N1X on D3D12, and ORT runtime
1.28.3.
### Motivation and Context
<!-- - Why is this change required? What problem does it solve?
- If it fixes an open issue, please link to the issue here. -->
The W3C WebNN WPT subtest `webnn/conformance_tests/relu.https.any.js`
"relu int32 4D tensor" failed on the WebGPU EP with "Failed to build
graph". WebNN disables CPU fallback, and WebGPU `Relu` had no int32
kernel, so the node was assigned to CPU and session creation failed.
Co-authored-by: Aditya Rastogi <adityar@ntdev.microsoft.com>
Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>
