[Feature] add lveval benchmark (#914)

* add lveval benchmark

* add LVEval readme file

* update LVEval readme file

* Update configs/eval_bluelm_32k_lveval.py

* Update configs/eval_llama2_7b_lveval.py

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Co-authored-by: yuantao <yuantao@infini-ai.com>
Co-authored-by: Mo Li <82895469+DseidLi@users.noreply.github.com>

opencompass/datasets/lveval/lveval_multifieldqa_en_mixup.py

+from datasets import Dataset, load_dataset
+
+from opencompass.registry import LOAD_DATASET
+
+from ..base import BaseDataset
+
+
+@LOAD_DATASET.register_module()
+class LVEvalmultifieldqaenDataset(BaseDataset):
+
+    @staticmethod
+    def load(**kwargs):
+        dataset = load_dataset(**kwargs)
+        split = 'test'
+        raw_data = []
+        for i in range(len(dataset[split])):
+            question = dataset[split]['input'][i]
+            context = dataset[split]['context'][i]
+            answers = dataset[split]['answers'][i]
+            confusing_facts = dataset[split]['confusing_facts'][i]
+            answer_keywords = dataset[split]['answer_keywords'][i]
+            answers_with_ak = answers + [answer_keywords]
+            raw_data.append({
+                'input': question,
+                'context': context,
+                'answers': answers_with_ak,
+                'confusing_facts': confusing_facts,
+                'answer_keywords': answer_keywords,
+            })
+        dataset[split] = Dataset.from_list(raw_data)
+        return dataset

opencompass/datasets/lveval/lveval_multifieldqa_zh_mixup.py

+from datasets import Dataset, load_dataset
+
+from opencompass.registry import LOAD_DATASET
+
+from ..base import BaseDataset
+
+
+@LOAD_DATASET.register_module()
+class LVEvalmultifieldqazhDataset(BaseDataset):
+
+    @staticmethod
+    def load(**kwargs):
+        dataset = load_dataset(**kwargs)
+        split = 'test'
+        raw_data = []
+        for i in range(len(dataset[split])):
+            question = dataset[split]['input'][i]
+            context = dataset[split]['context'][i]
+            answers = dataset[split]['answers'][i]
+            confusing_facts = dataset[split]['confusing_facts'][i]
+            answer_keywords = dataset[split]['answer_keywords'][i]
+            answers_with_ak = answers + [answer_keywords]
+            raw_data.append({
+                'input': question,
+                'context': context,
+                'answers': answers_with_ak,
+                'confusing_facts': confusing_facts,
+                'answer_keywords': answer_keywords,
+            })
+        dataset[split] = Dataset.from_list(raw_data)
+        return dataset