🚨🚨 Fix and simplify attention implementation dispatch and subconfigs handling (#39423)

* first try

* Update modeling_utils.py

* Update modeling_utils.py

* big refactor

* Update modeling_utils.py

* style

* docstrings and simplify inner workings of configs

* remove all trace of _internal

* Update modeling_utils.py

* fix logic error

* Update modeling_utils.py

* recursive on config

* Update configuration_utils.py

* fix

* Update configuration_dpt.py

* Update configuration_utils.py

* Update configuration_utils.py

* Update modeling_idefics.py

* Update modeling_utils.py

* fix for old models

* more old models fixup

* Update modeling_utils.py

* Update configuration_utils.py

* Remove outdated test

* remove the deepcopy!! 🥵🥵

* Update test_modeling_gpt_bigcode.py

* fix qwen dispatch

* restrict to only models supporting it

* style

* switch name

* Update modeling_utils.py

* Update modeling_utils.py

* add tests!

* fix

* rypo

* remove bad copies

* fix

* Update modeling_utils.py

* additional check

* Update modeling_utils.py

* Update modeling_utils.py

* Update modeling_utils.py

* Update modeling_utils.py

* Update modeling_utils.py

* fix

* skip

tests/models/gpt_bigcode/test_modeling_gpt_bigcode.py

@@ -542,6 +542,8 @@ class GPTBigCodeMQATest(unittest.TestCase):
             attn_pdrop=0,
             resid_pdrop=0,
         )
+        # We need to set it here as it's normally set by the Model's __init__
+        config._attn_implementation = "sdpa"
         return GPTBigCodeAttention(config)
 
     @parameterized.expand([(seed, is_train_mode) for seed in range(5) for is_train_mode in [True, False]])