[Whisper] Refactor forced_decoder_ids & prompt ids (#28687)

* up

* Fix more

* Correct more

* Fix more tests

* fix fast tests

* Fix more

* fix more

* push all files

* finish all

* make style

* Fix timestamp wrap

* make style

* make style

* up

* up

* up

* Fix lang detection behavior

* Fix lang detection behavior

* Add lang detection test

* Fix lang detection behavior

* make style

* Update src/transformers/models/whisper/generation_whisper.py
Co-authored-by: Sanchit Gandhi <93869735+sanchit-gandhi@users.noreply.github.com>

* better error message

* make style tests

* add warning

---------
Co-authored-by: Sanchit Gandhi <93869735+sanchit-gandhi@users.noreply.github.com>

tests/pipelines/test_pipelines_automatic_speech_recognition.py

@@ -1451,6 +1451,7 @@ class AutomaticSpeechRecognitionPipelineTests(unittest.TestCase):
         # Original model wasn't trained with timestamps and has incorrect generation config
         pipe.model.generation_config = GenerationConfig.from_pretrained("openai/whisper-large-v2")
 
+        # the audio is 4 seconds long
         audio = hf_hub_download("Narsil/asr_dummy", filename="hindi.ogg", repo_type="dataset")
 
         out = pipe(
@@ -1460,11 +1461,8 @@ class AutomaticSpeechRecognitionPipelineTests(unittest.TestCase):
         self.assertEqual(
             out,
             {
-                "chunks": [
-                    {"text": "", "timestamp": (18.94, 0.02)},
-                    {"text": "मिर्ची में कितने विभिन्न प्रजातियां हैं", "timestamp": (None, None)},
-                ],
                 "text": "मिर्ची में कितने विभिन्न प्रजातियां हैं",
+                "chunks": [{"timestamp": (0.58, None), "text": "मिर्ची में कितने विभिन्न प्रजातियां हैं"}],
             },
         )