Add async checkpointing for kd distributed and single device recipes

[ankitageorge]

Context

What is the purpose of this PR? Is it to

• [ x] add a new feature
• fix a bug
• update tests and/or documentation
• other (please add here)

Please link to any issues this PR addresses.

Changelog

What are the changes made in this PR?

• Add async checkpointing behind the enable_async_checkpointing flag for kd distributed and single device recipes

Test plan

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• [ x] add unit tests for any new functionality
• update docstrings for any new or updated methods or classes
• [ x] run unit tests via pytest tests
• [x ] run recipe tests via pytest tests -m integration_test
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UX

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• [x ] I did not change any public API
• I have added an example to docs or docstrings

[pytorch-bot]

🔗 Helpful Links

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