fix: add missing docstrings to data pipeline utility functions

[stanley1208]

What does this PR do?

Add missing docstrings to 4 data pipeline utility functions in audio_to_text_dataset.py, per Contributor guidelines which state:

"Include docstrings for every class and method exposed to the user"

These functions are critical parts of the ASR data pipeline (dataset creation, bucketing, code-switching) and were missing documentation.

Functions documented:

• get_code_switched_dataset — Creates multilingual code-switched datasets
• convert_to_config_list — Normalizes manifest paths into ListConfig format for bucketing
• get_chain_dataset — Chains bucketed datasets with configurable bucketing strategy
• calc_bucketing_batch_sizes — Calculates adaptive batch sizes for bucketed training

Collection: ASR

Changelog

• Add docstrings to 4 undocumented data pipeline functions in audio_to_text_dataset.py

Before your PR is "Ready for review"

• Make sure you read and followed Contributor guidelines
• Did you write any new necessary tests? (N/A — docstrings only)
• Did you add or update any necessary documentation?

PR Type:

• Documentation

[stanley1208]

@nithinraok Ready for review — adds missing docstrings to 4 key data pipeline functions per CONTRIBUTING.md guidelines. Thanks!