ORDER OF REVIEWS:
1. #1108
2. #1103 
3. #1109 <- current
PR
4. #1110


SUMMARY:
Refactor `initialize_model_from_path` to decouple `training_args`
dependent logic and oneshot (non-training_args) logic.

TEST PLAN:
* Pass all tests
* search `initialize_model_from_path` using `grep`

ORDER OF REVIEWS:
1. #1108
2. #1103 
3. #1109
4. #1110 <- current
PR


SUMMARY:
* Create a class to decouple dependency to `main`. Class `Oneshot`
consists of pre-processing, carrying out oneshot logic and
post-processing
* Move the oneshot class and method under
`llmcompressor/entrypoints/oneshot.py`.
* Add ReadMe in `/llmcompressor/entrypoints` for info on oneshot
* Delete oneshot logic from `/finetune` directory, add deprecation
warning
* Remove apply used only for stagerunner oneshot pathway in session.py
and session_function.py
* Add oneshot only calibration dataloader logic
* Add a return variable of `model: PretrainedModel` for `def oneshot`.
* Make oneshot carryout logic independent of `TrainingArguments`
* remove `overwrite_output_dir` as oneshot input arg -> only used for
`TrainingArguments`
* Update README on `/finetune` path. Remove `oneshot` logic and `oneshot
with fsdp`
* Update `wrap_save_pretrained` logic to run only if not updated already
-> used for stage runner to avoid double wrapping



Entrypoints: 
```python3
from llmcompressor import oneshot
oneshot(**kwargs) # calls Oneshot
```

or 

```python3
from llmcompressor import Oneshot
oneshot = Oneshot(**kwargs)
oneshot() # preprocesss, carries out logic and post process
```


TEST PLAN:
Pass all tests and examples. 
Verified
https://github.com/vllm-project/llm-compressor/blob/main/examples/quantization_2of4_sparse_w4a16/llama7b_sparse_w4a16.py
works as expected.

FOLLOW UPS:
* Stage runner removal
* Update entrypoints folder with train, eval, predict, etc.

---------

Signed-off-by: George Ohashi <george@neuralmagic.com>
Signed-off-by: George <george@neuralmagic.com>