Update datasets task tags to align tags with models (#4067)

* update tasks list

* update tags in dataset cards

* more cards updates

* update dataset tags parser

* fix multi-choice-qa

* style

* small improvements in some dataset cards

* allow certain tag fields to be empty

* update vision datasets tags

* use multi-class-image-classification and remove other tags

Commit from https://github.com/huggingface/datasets/commit/edb4411d4e884690b8b328dba4360dbda6b3cbc8

README.md

@@ -136,7 +136,7 @@ task_categories:
   cweb:
   - text-retrieval
   eli5:
-  - question-answering
+  - text2text-generation
   - text-retrieval
   fever:
   - text-classification
@@ -148,10 +148,12 @@ task_categories:
   - question-answering
   - text-retrieval
   structured_zeroshot:
-  - sequence-modeling
+  - text-generation
+  - fill-mask
   - text-retrieval
   trex:
-  - sequence-modeling
+  - text-generation
+  - fill-mask
   - text-retrieval
   triviaqa_support_only:
   - question-answering
@@ -159,7 +161,8 @@ task_categories:
   wned:
   - text-retrieval
   wow:
-  - sequence-modeling
+  - text-generation
+  - fill-mask
   - text-retrieval
 task_ids:
   aidayago2:
@@ -171,7 +174,7 @@ task_ids:
   eli5:
   - abstractive-qa
   - document-retrieval
-  - open-domain-qa
+  - open-domain-abstractive-qa
   fever:
   - document-retrieval
   - fact-checking