* Add precompute_ref_log_probs to config schema
* chore: add description for config
* Add test for precompute_ref_log_probs and move to training args
* useing precompute logprobs as the default slows down CI as it has to precompute
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Co-authored-by: NanoCode012 <nano@axolotl.ai>
Co-authored-by: Wing Lian <wing@axolotl.ai>