Add nemo retriever embeddings integration

[ChrisJar]

Description

Please include a summary of the change and which issue is fixed. Please also include relevant motivation and context. List any dependencies that are required for this change.

Fixes # (issue)

Type of Change

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• New feature (non-breaking change which adds functionality)

How Has This Been Tested?

Please describe the tests that you ran to verify your changes. Provide instructions so we can reproduce. Please also list any relevant details for your test configuration

• Added new unit/integration tests
• Added new notebook (that tests end-to-end)
• I stared at the code and made sure it makes sense

TODO:

• [ x ] I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added Google Colab support for the newly added notebooks.
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• I ran make format; make lint to appease the lint gods

[logan-markewich]

Does nemo support batch embeddings? If so, _get_text_embeddings should use it

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[logan-markewich]

@ChrisJar does nemo support batch embeddings? Right now it runs sequentially which will be very slow

[logan-markewich]

Going to close this one out for now, its quite outdated at this point

If its still an issue, please raise an updated PR

Sorry for letting this one sit for so long!