[Feature] add global retriever config (#842)

* add global retriever config

* give zero shot overwrite example

* give zero shot overwrite example

---------
Co-authored-by: Lei Fei <SENSETIME\leifei1@cn3114002087l.domain.sensetime.com>
Co-authored-by: Leymore <zfz-960727@163.com>

configs/eval_mmlu_with_zero_retriever_overwritten.py

+from mmengine.config import read_base
+from opencompass.openicl.icl_retriever import ZeroRetriever
+from copy import deepcopy
+
+with read_base():
+    from .models.qwen.hf_qwen_7b_chat import models
+    from .datasets.mmlu.mmlu_gen_4d595a import mmlu_datasets # this is a dataset evaluated with 5-shot
+
+
+datasets = []
+for d in mmlu_datasets:
+    d = deepcopy(d)
+    d['infer_cfg']['retriever'] = dict(type=ZeroRetriever)
+    datasets.append(d)