[Refactor] Benchmark: Add typed DatasetArgs/Loader registry and CPU dataset unit tests (#19147)

Co-authored-by: Liangsheng Yin <lsyincs@gmail.com>

scripts/playground/bench_speculative.py

@@ -20,7 +20,8 @@ import requests
 from transformers import AutoTokenizer
 
 from sglang.bench_serving import benchmark, set_global_args
-from sglang.benchmark.datasets import DatasetRow, sample_mmmu_requests
+from sglang.benchmark.datasets import DatasetRow
+from sglang.benchmark.datasets.mmmu import sample_mmmu_requests
 from sglang.srt.server_args import ServerArgs
 from sglang.test.test_utils import (
     DEFAULT_TIMEOUT_FOR_SERVER_LAUNCH,