trunk/284bad2bac9d4f10515c57eabb5bc2c54baeb551: [inductor] extract _emit_triton_kernel_compile_metric helper (#182978)

Summary:

Pulls the per-kernel compile_time_us emission boilerplate (build dict -> _add_triton_kernel_info + MetricsContext.add_top_n) out of AsyncCompile.triton's two callsites (parallel-compile get_result and synchronous fallback) into a standalone helper. Pure refactor; behavior at the existing callsites is unchanged.

The helper docstring also calls out a small pre-existing quirk left intact: when kernel.autotune_cache_info is None or {}, the metric still reaches _triton_kernel_metrics, but the kernel attribute itself is not updated (only the truthy case mutates in place via the or {} reference).

Authored by Claude.

Test Plan: buck test fbcode//mode/opt fbcode//caffe2/test/inductor:async_compile

Differential Revision: D104186703

Pull Request resolved: