Add support for fewshot and apply chat template lm_eval functionality (#1180)

* Add support for multiturn fewshot examples and chat templates

Added two new arguments to the evaluation script: `--fewshot-as-multiturn` and `--apply-chat-template` which correspond to lm_eval options of similar names and are very often used to ensure apples-to-apples comparisons of lm_evaluation results

* Add HF overrides for methods needed by added options

* don't add duplicate bos

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Co-authored-by: Awni Hannun <awni@apple.com>

.circleci/config.yml

@@ -32,7 +32,7 @@ jobs:
             pip install --upgrade pip
             pip install unittest-xml-reporting
             cd llms/
-            pip install -e ".[testing]"
+            pip install -e ".[test]"
       - run:
           name: Run Python tests
           command: |