Tests: move generate tests to the right mixin and delete redundant tests (#34464)

* tmp commit

* tmp commit

* cull overwrites of deleted tests

* typo

* more specific docstring

* make fixup

* parameterize at the top?

* correction

* more deletions :D

* tmp commit

* for VLMs too

* fix _check_outputs

* test nit

* make fixup

* fix another flaky

* test_generate_from_inputs_embeds -- handle missing attention mask

tests/models/bart/test_modeling_bart.py

@@ -1532,8 +1532,3 @@ class BartStandaloneDecoderModelTest(ModelTesterMixin, GenerationTesterMixin, un
     @unittest.skip
     def test_save_load_fast_init_from_base(self):
         pass
-
-    @unittest.skip(reason="Generate needs input ids")
-    def test_inputs_embeds_matches_input_ids_with_generate(self):
-        # generate only works with input ids for bartforcausalLM
-        pass