Remove low_cpu_mem_usage and _fast_init (#36963)

* Remove low_cpu_mem_usage and _fast_init

* Update deepspeed.py

* Update modeling_utils.py

* remove the first 2 tests everywhere

* Update test_modeling_common.py

* remove what was remaining about fast_init

* fix logic and simplify

* mismatched keys logic update

* Update modeling_utils.py

* Update modeling_utils.py

* Update modeling_utils.py

* Update modeling_utils.py

* fix 2 models init_weights

* extend to others

* remove grad

* Update modeling_fsmt.py

* init weights in tests

* style

* Update test_modeling_fsmt.py

* more old models

* fix more init_weights

* copies

* fix

* style

* Update modeling_lxmert.py

* fix inits

* more and more

* more

* should finalize

* style

* Update modeling_dinov2_with_registers.py

* fix

* Update modeling_encoder_decoder.py

* fix

* style

* Update modeling_lxmert.py

* post rebase cleanup

* Update modeling_informer.py

* back to start for device

* fix

* add test to detect all failing cases correctly

* Update test_modeling_common.py

* fix

* fix

* sam

* style

* Update modeling_maskformer_swin.py

* CIs

* CIs

* remove test - will add it on separate PR

* fix

* fix

* Update modeling_sam.py

* CIs

* CIs

* CIs

* convnext

* suggestions

* CIs

* fix copies after merge

---------

Co-authored-by: Yih-Dar <2521628+ydshieh@users.noreply.github.com>

tests/models/instructblip/test_modeling_instructblip.py

@@ -216,14 +216,6 @@ class InstructBlipVisionModelTest(ModelTesterMixin, unittest.TestCase):
     def test_training_gradient_checkpointing_use_reentrant_false(self):
         pass
 
-    @unittest.skip(reason="InstructBlipVisionModel has no base class and is not available in MODEL_MAPPING")
-    def test_save_load_fast_init_from_base(self):
-        pass
-
-    @unittest.skip(reason="InstructBlipVisionModel has no base class and is not available in MODEL_MAPPING")
-    def test_save_load_fast_init_to_base(self):
-        pass
-
     @slow
     def test_model_from_pretrained(self):
         model_name = "Salesforce/instructblip-flan-t5-xl"
@@ -522,14 +514,6 @@ class InstructBlipForConditionalGenerationDecoderOnlyTest(ModelTesterMixin, Gene
     def test_model_get_set_embeddings(self):
         pass
 
-    @unittest.skip(reason="There's no base InstructBlipModel")
-    def test_save_load_fast_init_from_base(self):
-        pass
-
-    @unittest.skip(reason="There's no base InstructBlipModel")
-    def test_save_load_fast_init_to_base(self):
-        pass
-
     @unittest.skip(
         "InstructBLIP cannot generate only from input ids, and requires pixel values in all cases to be present"
     )