Added NorEval, a novel Norwegian benchmark (#2919)

* added noreval

* added a checklist for noreval

* run pre-commit

* changed imports and added short noreval description

* fixed norsumm path

* refactored multi-folder tasks

* refactored multi-folder tasks

lm_eval/tasks/noreval/tatoeba/tatoeba_nob_eng/tatoeba_nob_eng_p0.yaml

+tag: tatoeba_nob_eng
+dataset_name: eng-nob
+doc_to_target: sourceString
+task: tatoeba_nob_eng_p0
+include: ../_tatoeba_yaml
+doc_to_text: "Bokmål: {{targetString}}\nEngelsk:"

lm_eval/tasks/noreval/tatoeba/tatoeba_nob_eng/tatoeba_nob_eng_p1.yaml

+tag: tatoeba_nob_eng
+dataset_name: eng-nob
+doc_to_target: sourceString
+task: tatoeba_nob_eng_p1
+include: ../_tatoeba_yaml
+doc_to_text: "Oversett følgende setning til engelsk: {{targetString}}\nEngelsk:"

lm_eval/tasks/noreval/tatoeba/tatoeba_nob_eng/tatoeba_nob_eng_p2.yaml

+tag: tatoeba_nob_eng
+dataset_name: eng-nob
+doc_to_target: sourceString
+task: tatoeba_nob_eng_p2
+include: ../_tatoeba_yaml
+doc_to_text: "Gi en engelsk oversettelse av denne setningen: {{targetString}}\nEngelsk:"

lm_eval/tasks/noreval/tatoeba/tatoeba_nob_eng/tatoeba_nob_eng_p3.yaml

+tag: tatoeba_nob_eng
+dataset_name: eng-nob
+doc_to_target: sourceString
+task: tatoeba_nob_eng_p3
+include: ../_tatoeba_yaml
+doc_to_text: "Hva blir \"{{targetString}}\" på engelsk?\nEngelsk:"