[moe training] update readme with links, cleanup

[danielvegamyhre]

• For API/function references, add links to the code
• Improve formatting for better readability
• Include convenience APIs for specific recipes
• Update code examples

[pytorch-bot]

🔗 Helpful Links

🧪 See artifacts and rendered test results at hud.pytorch.org/pr/pytorch/ao/3239

• 📄 Preview Python docs built from this PR

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

✅ You can merge normally! (1 Unrelated Failure)

As of commit cfed23a with merge base 53b5efd ():

BROKEN TRUNK - The following job failed but were present on the merge base:

👉 Rebase onto the `viable/strict` branch to avoid these failures

• Run 1xH100 Tests / test (H100, linux.aws.h100, --pre torch torchvision torchaudio fbgemm-gpu-genai --index-url https... / linux-job (gh) (trunk failure)
  test/integration/test_load_and_run_checkpoint.py::TestLoadAndRunCheckpoint::test_deprecated_hf_models_model_info3

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