Add vocab masks to Whisper export with beam search (#16180)
### Description
This PR adds flags for exporting Whisper with vocab masks for logits
processing. This PR also sets `input_features` back to FP32 precision
for the user and casts `input_features` to FP16 precision when needed.
### Motivation and Context
This helps enable specific logits processing for the exported Whisper
model.
