feat(triton): add rms_norm operator

[fuyou4546]

Summary

• Add RMSNorm operator on Triton backend (src/triton/ops/rms_norm/{rms_norm.py, build.py, rms_norm.h})

Motivation

Add an RMSNorm operator on the Triton backend, supporting fp16, bf16, and fp32.
One program per row with fp32 accumulation.

Closes N/A

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 (requires a ! in the Conventional Commits prefix or a BREAKING CHANGE: footer)

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

python -m pytest tests -m smoke -q
.................ss..ss....s................................ssssss..ss................                                                                                                                    [100%]
73 passed, 13 skipped, 20864 deselected in 3.17s

Test Results on Supported Platforms

Platform	Affected	Build / Smoke Result	Full Result / Notes
NVIDIA	√	Successfully installed InfiniOps-0.1.0 / 73 passed, 13 skipped, 20864 deselected	36 passed, 72 deselected
Iluvatar
MetaX
Cambricon
Moore
Ascend

Full `pytest` output (optional)

 pytest tests/test_rms_norm.py -k "cuda-8"
======== test session starts ========
platform linux -- Python 3.12.0, pytest-9.0.3, pluggy-1.6.0
rootdir: /home/zhangshuo/projects/InfiniTensor/InfiniOps
configfile: pyproject.toml
plugins: xdist-3.8.0, cov-7.1.0
collected 108 items / 72 deselected / 36 selected                                                                                                                                                               

tests/test_rms_norm.py ....................................                                                                                                                                               [100%]

======== 36 passed, 72 deselected in 0.59s ========

Benchmark / Performance Impact

N/A

Notes for Reviewers

Depends on the AOT infrastructure in feat/triton-backend.