[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>

src/transformers/testing_utils.py

@@ -227,6 +227,12 @@ def require_torch_non_multigpu(test_case):
         return test_case
 
 
+# this is a decorator identical to require_torch_non_multigpu, but is used as a quick band-aid to
+# allow all of examples to be run multi-gpu CI and it reminds us that tests decorated with this one
+# need to be ported and aren't so by design.
+require_torch_non_multigpu_but_fix_me = require_torch_non_multigpu
+
+
 def require_torch_tpu(test_case):
     """
     Decorator marking a test that requires a TPU (in PyTorch).