Whisper encoder + No 30 second padding

[farzadab]

This PR enables Whisper model for training and inference, without the need for full 30 second padding.

I verified that the inference works with:

$ python -m ultravox.tools.infer_tool  -T 32 -n 10 -d boolq_in --asr \
    -m wandb://fixie/ultravox/model-llama3_whisper_s__gs__cont_lora_gs_ai_constant__longest_pad:v1

--- Sample 0 ---
Q: Transcribe <|audio|> ["do iran and afghanistan speak the same language?"]
A: Do Iran and Afghanistan speak the same language?
X: do iran and afghanistan speak the same language? [wer: 0.00, avg: 0.00]
--- Sample 1 ---
Q: Transcribe <|audio|> ["do good samaritan laws protect those who help at an accident?"]
A: Do good Samaritan laws protect those who help at an accident?
X: do good samaritan laws protect those who help at an accident? [wer: 0.00, avg: 0.00]
--- Sample 2 ---
Q: Transcribe <|audio|> ["is windows movie maker part of windows essentials?"]
A: Is Windows Movie Maker part of windows essentials?
X: is windows movie maker part of windows essentials? [wer: 0.00, avg: 0.00]
--- Sample 3 ---
Q: Transcribe <|audio|> ["is confectionary sugar the same as powdered sugar?"]
A: Is confectionary sugar the same as powdered sugar?
X: is confectionary sugar the same as powdered sugar? [wer: 0.00, avg: 0.00]
--- Sample 4 ---
Q: Transcribe <|audio|> ["is elder scrolls online the same as skyrim?"]
A: Is elder scrolls Online the same as Skyrim?
X: is elder scrolls online the same as skyrim? [wer: 0.00, avg: 0.00]
--- Sample 5 ---
Q: Transcribe <|audio|> ["can you use oyster card at epsom station?"]
A: Can you use Oyster card at Upminster station?
X: can you use oyster card at epsom station? [wer: 0.12, avg: 0.02]
--- Sample 6 ---
Q: Transcribe <|audio|> ["will there be a season 4 of da vinci's demons?"]
A: Will there be a season four of Downton Abbey?
X: will there be a season 4 of da vinci's demons? [wer: 0.45, avg: 0.08]
...