Add support for splitting in_features in linear layers

[metascroy]

This PR:

• Moves SplitLinearModule to a separate utils.py and extends it to support splitting in_features. I did not find splitting in_features worked very well, at least in my initial experiments.
• Updates readme with latest setting recommendations for Llama1B

[pytorch-bot]

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❌ 2 New Failures

As of commit 47f0c44 with merge base 5a594a7 ():

NEW FAILURES - The following jobs have failed:

• Check Labels / Check labels (gh)
  RuntimeError: Error checking labels: PR does not have required labels
• pull / test-llava-runner-linux / linux-job (gh)
  RuntimeError: Command docker exec -t 0306fdffce30f5f30e137bd28a5936d03d3188b23152b69fadc87811d7a0525c /exec failed with exit code 139

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