Add tags parameter support to @register_benchmark decorator

[jialiangqu]

Implements the feature requested in PR #647 comments - allows users to specify tags directly in the decorator

Tags from the decorator are merged with auto-detected tags (from AST analysis and name-based heuristics). Added REGISTERED_BACKEND_TAGS global dict to store decorator tags, and updated the tagging system in run.py to merge all tag sources.

Apply a patch locally to test the new functionality
in tritonbench/operators/gemm/operator.py, add a dummy tag to triton backend

    @register_benchmark(tags=["dummy"])
    def triton_tutorial_matmul(self, a, b, bias) -> Callable:
        if bias is not None:
            return lambda: triton_tutorial_matmul_kernel(a, b) + bias
        else:
            return lambda: triton_tutorial_matmul_kernel(a, b)

run the analyzer to see it appears

$ python benchmarks/tagging/run.py --op gemm

{'gemm': {'pt2_triton_matmul': {'tags': ['pt2']}, 'pt2_matmul_maxautotune': {'tags': ['pt2']}, 'pt2_cutlass_matmul': {'tags': ['pt2', 'cutlass']}, 'matmul_decompose_k': {'tags': ['pt2']}, 'triton_tutorial_matmul': {'tags': ['dummy', 'triton'], 'kernels': ['matmul_kernel']}, 'matmul_partition_k': {'tags': ['triton'], 'kernels': ['_matmul_partition_k', '_reduce']}, 'triton_persistent_matmul': {'tags': []}, 'triton_tma_persistent_matmul': {'tags': []}, 'triton_tma_persistent_cached_matmul': {'tags': []}, 'triton_ops_matmul': {'tags': ['triton'], 'kernels': ['_splitk_kernel']}, 'aten_matmul': {'tags': ['aten']}, 'aten_tunableop_matmul': {'tags': ['aten']}, 'hstu_triton_matmul': {'tags': []}, 'streamk_matmul': {'tags': ['triton'], 'kernels': ['streamk_amd_gemm']}}}

we can see dummy tag appears in triton_tutorial_matmul

[xuzhao9]

Can we remove the use of REGISTERED_BACKEND_TAGS? Instead, we can add it as a field of class BenchmarkOperatorBackend

[xuzhao9]

Thanks for the contribution!
For maintenance, we want to minimize the use the global dictionaries, instead we want to use the BenchmarkOperatorBackend class to manage all tags of the backend. Can you help refactor the code?