Move RLHF out of modules

[SalmanMohammadi]

Context

What is the purpose of this PR? Is it to

• add a new feature
• fix a bug
• update tests and/or documentation
• other (refactor)

closes #1590

Test plan

Please make sure to do each of the following if applicable to your PR. (If you're not sure about any one of these just ask and we will happily help. We also have a contributing page for some guidance on contributing.)

• run pre-commit hooks and linters (make sure you've first installed via pre-commit install)
• add unit tests for any new functionality
• update docstrings for any new or updated methods or classes
• run unit tests via pytest tests
• run recipe tests via pytest tests -m integration_test
• manually run any new or modified recipes with sufficient proof of correctness
• include relevant commands and any other artifacts in this summary (pastes of loss curves, eval results, etc.)

UX

If your function changed a public API, please add a dummy example of what the user experience will look like when calling it.
Example of docstring:

torchtune/torchtune/modules/vision_transformer.py

Line 285 in 6a7951f

Examples:

Example in our docs: https://pytorch.org/torchtune/main/tutorials/qat_finetune.html#applying-qat-to-llama3-models

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

[pytorch-bot]

🔗 Helpful Links

🧪 See artifacts and rendered test results at hud.pytorch.org/pr/pytorch/torchtune/1591

• 📄 Preview Python docs built from this PR

Note: Links to docs will display an error until the docs builds have been completed.

✅ No Failures

As of commit 2adc6a6 with merge base 6820089 ():
💚 Looks good so far! There are no failures yet. 💚

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[codecov-commenter]

Codecov Report

Attention: Patch coverage is 57.14286% with 6 lines in your changes missing coverage. Please review.

Project coverage is 72.88%. Comparing base (6820089) to head (2adc6a6).

Files with missing lines	Patch %	Lines
recipes/lora_dpo_distributed.py	0.00%	2 Missing ⚠️
recipes/lora_dpo_single_device.py	0.00%	2 Missing ⚠️
recipes/ppo_full_finetune_single_device.py	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1591      +/-   ##
==========================================
+ Coverage   72.87%   72.88%   +0.01%     
==========================================
  Files         290      290              
  Lines       14252    14249       -3     
==========================================
  Hits        10386    10386              
+ Misses       3866     3863       -3     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[RdoubleA]

you beautiful man