New run glue script (#7917)

* Start simplification

* More progress

* Finished script

* Address comments and update tests instructions

* Wrong test

* Accept files as inputs and fix test

* Update src/transformers/trainer_utils.py

Co-authored-by: Julien Chaumond <chaumond@gmail.com>

* Fix labels and add combined score

* Add special labels

* Update TPU command

* Revert to old label strategy

* Use model labels

* Fix for STT-B

* Styling

* Apply suggestions from code review

Co-authored-by: Thomas Wolf <thomwolf@users.noreply.github.com>

* Code styling

* Fix review comments

Co-authored-by: Julien Chaumond <chaumond@gmail.com>
Co-authored-by: Thomas Wolf <thomwolf@users.noreply.github.com>

examples/test_examples.py

@@ -67,10 +67,10 @@ class ExamplesTests(TestCasePlus):
         testargs = f"""
             run_glue.py
             --model_name_or_path distilbert-base-uncased
-            --data_dir ./tests/fixtures/tests_samples/MRPC/
             --output_dir {tmp_dir}
             --overwrite_output_dir
-            --task_name mrpc
+            --train_file ./tests/fixtures/tests_samples/MRPC/train.csv
+            --validation_file ./tests/fixtures/tests_samples/MRPC/dev.csv
             --do_train
             --do_eval
             --per_device_train_batch_size=2