Fix for incorrect computation of batched alignment in transducers
# What does this PR do ?

The original code had a bug because of which whenever at least one batch element predicted non-blank symbol, all blank elements would duplicate the last prediction in their `.alignments` variable.

Additionally, I've unified `_greedy_decode_blank_as_pad` and `_greedy_decode_masked` into a single function with an if check. The two methods had 99% of the same code except 5 lines or so, so imo it does not make sense to have them as fully separate code paths. Please let me know if for some reason we don't want to have this change.

**Collection**: ASR

# Changelog 
- Add specific line by line info of high level changes in this PR.

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```python
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# Additional Information
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