feat: align elu with PyTorch Python API

[voltjia]

Summary

• Expose one primary elu(input, alpha, out) interface matching PyTorch's public attribute.
• Keep the previous ATen-derived scale and input_scale interface as a [[deprecated]] compatibility overload.

Motivation

The public InfiniOps ELU interface exposed internal ATen implementation parameters that do not appear in torch.nn.functional.elu. The earlier revision also added an alpha=1.0 convenience overload; this revision removes it to keep the overload set minimal.

No standalone issue is associated with this alignment follow-up.

Type of Change

• feat - new feature / new operator / new platform
• fix - bug fix
• perf - performance improvement (no behavioral change)
• refactor - code restructuring without behavior change
• test - adding or fixing tests only
• docs - documentation only
• build / ci - build system or CI configuration
• chore - tooling, formatting, or other non-code changes
• Breaking change

Platforms Affected

• CPU (WITH_CPU)
• NVIDIA (WITH_NVIDIA)
• Iluvatar (WITH_ILUVATAR)
• MetaX (WITH_METAX)
• Cambricon (WITH_CAMBRICON)
• Moore (WITH_MOORE)
• Ascend (WITH_ASCEND)
• PyTorch C++ bindings (WITH_TORCH)
• Build system / CMake / CI
• Python bindings / user-facing API

Smoke Test Result

Host: ssh nvidia
Image: accelerator-dev/nvidia:latest
PyTorch: 2.10.0a0+b4e4ee8

cmake ... -DWITH_CPU=ON -DWITH_NVIDIA=ON -DWITH_TORCH=ON \
  -DINFINI_OPS_OPS=elu -DINFINI_OPS_TORCH_OPS=elu
cmake --build build-nvidia --target ops -j 16
Build passed; codegen emitted 1 ATen implementation overload.

python -m pytest tests/test_generate_wrappers.py -q
13 passed

python -m pytest tests/test_torch_ops.py -k elu --devices cpu nvidia -q
18 passed

Test Results on Supported Platforms

Platform	Affected	Build / Smoke Result	Full Result / Notes
CPU	Yes	targeted build passed	Primary and deprecated paths passed
NVIDIA	Yes	targeted build passed	Primary and deprecated paths passed
Iluvatar	No	N/A - not affected	N/A - not affected
MetaX	No	N/A - not affected	N/A - not affected
Cambricon	No	N/A - not affected	N/A - not affected
Moore	No	N/A - not affected	N/A - not affected
Ascend	No	N/A - not affected	N/A - not affected

Benchmark / Performance Impact

N/A. The primary interface delegates to the existing ATen implementation with scale=1.0 and input_scale=1.0.

Notes for Reviewers

API alignment

Interface	Signature	Alignment basis
InfiniOps primary	elu(input, alpha, out)	Matches PyTorch's out-of-place public attribute; explicit out remains last per CONTRIBUTING.md.
PyTorch public API	F.elu(input, alpha=1.0, inplace=False)	Pinned PyTorch source
Deprecated compatibility	elu(input, alpha, scale, input_scale, out)	Preserves the pre-alignment ATen-derived interface for migration.

• C++ callers pass alpha=1.0 explicitly when they want the PyTorch default.
• The existing test_op path was extended instead of adding another test function.
• Ruff 0.15.22 and clang-format 21.1.8 checks passed.