[`GPTQ`, `CompressedTensors`] Fix unsafe imports and metada check
Author: vasqu
Pull request: yes

# What does this PR do?
Fixes some unsafe imports for GPTQ and CompressedTensors as well as an unsafe metadata check for GPTQ, i.e. metadata can't be checked if the package doesn't exist...

I tried looking into integrating the env validation function before even creating the quantizers but that would require a complete restructure, especially since the env is checked after creation to get additional info like device map etc. So I kept it as simple as I could and wrapped the unsafe stuff.

Minimal reproducible script to trigger gptq errors (when optimum is not installed):
```python
from transformers import AutoModelForCausalLM, AutoTokenizer, GPTQConfig


model_id = "facebook/opt-125m"
tokenizer = AutoTokenizer.from_pretrained(model_id)
dataset = ["auto-gptq is an easy-to-use model quantization library with user-friendly apis, based on GPTQ algorithm."]
gptq_config = GPTQConfig(bits=4, dataset=dataset, tokenizer=tokenizer)


quantized_model = AutoModelForCausalLM.from_pretrained(model_id, device_map="auto", quantization_config=gptq_config)
```


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Fixes #34765


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Comments:
Thanks for the fix @vasqu, LGTM !

The docs for this PR live [here](https://moon-ci-docs.huggingface.co/docs/transformers/pr_34815). All of your documentation changes will be reflected on that endpoint. The docs are available until 30 days after the last update.

@ArthurZucker 
See my comments above: 
> I tried looking into integrating the env validation function before even creating the quantizers but that would require a complete restructure, especially since the env is checked after creation to get additional info like device map etc. So I kept it as simple as I could and wrapped the unsafe stuff.

The problem is some quantizers need additional information that is not available at creation; another option I could see it to add a post_init to create those unsafe parts :)

gentle ping @ArthurZucker 

Not sure if it was fixed by recent quantizer compressed changes, let's resolve conflicts and good to merge

Forgot about this PR myself :sweat_smile: should be good to merge now! Thx for the merges here, ci sometimes do be flaky tho

will merge it once the ci is green @vasqu 🤗