[github CI] add a multi-gpu job for all example tests (#8341)

* add a multi-gpu job for all example tests

* run only ported tests

* rename

* explain why env is re-activated on each step

* mark all unported/checked tests with @require_torch_non_multigpu_but_fix_me

* style

* Apply suggestions from code review

Co-authored-by: Sam Shleifer <sshleifer@gmail.com>

Co-authored-by: Sam Shleifer <sshleifer@gmail.com>

examples/deebert/test_glue_deebert.py

@@ -5,7 +5,7 @@ import unittest
 from unittest.mock import patch
 
 import run_glue_deebert
-from transformers.testing_utils import slow
+from transformers.testing_utils import require_torch_non_multigpu_but_fix_me, slow
 
 
 logging.basicConfig(level=logging.DEBUG)
@@ -26,6 +26,7 @@ class DeeBertTests(unittest.TestCase):
         logger.addHandler(stream_handler)
 
     @slow
+    @require_torch_non_multigpu_but_fix_me
     def test_glue_deebert_train(self):
 
         train_args = """