## Summary

This PR enables to use Liger Kernel's `_apply_liger_kernel_to_instance`
to init a fsdp worker model.

## Main Changes

1. Adding an option of using
`liger_kernel.transformers.AutoLigerKernelForCausalLM` to load a model
from pretained, instead of the default
`transformers.AutoModelForCausalLM`
2. Added a test case using configuration file
`tests/e2e/run_qwen_gsm8k_model_rm_liger_kernel.sh`

## Related Issue

#96 

## TODO

#97 optimize the memory usage when computing entropy & log_probs

https://github.com/volcengine/verl/blob/6d96fda3d47f057caaa8f494ca7804181903e911/verl/workers/actor/dp_actor.py#L94-L106

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Signed-off-by: Hongpeng Guo <hpguo@anyscale.com>