Add FSDP config for CPU RAM efficient loading through accelerate
Author: helloworld1
Pull request: yes

# What does this PR do?
Currently the environment variable `FSDP_CPU_RAM_EFFICIENT_LOADING` is being read [here](https://github.com/huggingface/transformers/blob/5080ab12c818d3875858ad37b667c00c6f09f094/src/transformers/modeling_utils.py#L137) but are set in `transformers` codebase. This change added option to set `FSDP_CPU_RAM_EFFICIENT_LOADING` through `cpu_ram_efficient_loading` FSDP option so jobs launched from `torchrun` or other means can take advantage of `FSDP_CPU_RAM_EFFICIENT_LOADING` through configs.

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Fixes # (issue)


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Comments:
The docs for this PR live [here](https://moon-ci-docs.huggingface.co/docs/transformers/pr_30002). All of your documentation changes will be reflected on that endpoint. The docs are available until 30 days after the last update.

Thanks for the suggestion. @muellerzr would you re-approve?

No need for a reapproval in those cases :) The green checkmark in transformers is end-all-be-all approval unless something radically changed outside that. cc @amyeroberts for final review

Running `make fixup` should resolve the code quality checks