[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/test_xla_examples.py

@@ -20,7 +20,7 @@ import unittest
 from time import time
 from unittest.mock import patch
 
-from transformers.testing_utils import require_torch_tpu
+from transformers.testing_utils import require_torch_non_multigpu_but_fix_me, require_torch_tpu
 
 
 logging.basicConfig(level=logging.DEBUG)
@@ -30,6 +30,7 @@ logger = logging.getLogger()
 
 @require_torch_tpu
 class TorchXLAExamplesTests(unittest.TestCase):
+    @require_torch_non_multigpu_but_fix_me
     def test_run_glue(self):
         import xla_spawn
 
@@ -81,6 +82,7 @@ class TorchXLAExamplesTests(unittest.TestCase):
             # Assert that the script takes less than 300 seconds to make sure it doesn't hang.
             self.assertLess(end - start, 500)
 
+    @require_torch_non_multigpu_but_fix_me
     def test_trainer_tpu(self):
         import xla_spawn