Iterative generation using Input embeds and past_key_values (#35890)

* Iterative generation using input embeds

* ruff fix

* Added Testcase

* Updated comment

* ♻️ Refactored testcase

* Skip test for these models

* Continue generation using input embeds and cache

* Skip generate_continue_from_embeds test

* Refactor `prepare_input_for_generation` func

* Continue generation using input embeds and cache

* Modular changes fix

* Overwrite 'prepare_inputs_for_generation' function

tests/models/clvp/test_modeling_clvp.py

@@ -334,6 +334,10 @@ class ClvpDecoderTest(ModelTesterMixin, GenerationTesterMixin, PipelineTesterMix
         loss = model(**inputs).loss
         loss.backward()
 
+    @unittest.skip(reason="Clvp `prepare_inputs_for_generation` function doesn't have cache position.")
+    def test_generate_continue_from_inputs_embeds(self):
+        pass
+
 
 class ClvpModelForConditionalGenerationTester:
     def __init__(self, parent, is_training=False):