Riva and k2 ASR WFST decoding (2)

[GNroy]

What does this PR do ?

Adds Riva and k2 WFST decoding options for ASR inference.

Collection: [ASR]

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• Add specific line by line info of high level changes in this PR.

Usage

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# Add a code snippet demonstrating how to use this 

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[github-actions[bot]]

This PR is stale because it has been open for 14 days with no activity. Remove stale label or comment or update or this will be closed in 7 days.

[github-actions[bot]]

This PR is stale because it has been open for 14 days with no activity. Remove stale label or comment or update or this will be closed in 7 days.

[github-actions[bot]]

This PR is stale because it has been open for 14 days with no activity. Remove stale label or comment or update or this will be closed in 7 days.

[artbataev]

@GNroy, can you please provide the instructions for testing this PR? A model + test set + LM/text to build LM with the sequence of required operations to build graphs/start decoding (both k2 and Riva). It may also be worth providing such information for users (make a section in the documentation).

[artbataev]

Please, also fix CodeQL suggestions - most of them seems to be valuable (e.g., 'except' clause does nothing but pass and there is no explanatory comment., This 'lambda' is just a simple wrapper around a callable object. Use that object directly., Variable wfst_path is not used. etc.)