Add option to not load pretrained weights in `AutoModel.from_pretrained()`
# 🚀 Feature request

Add option to not load pretrained weights in `AutoModel.from_pretrained()`
analogous to `pretrained=` in `timm.create_model(model_name, pretrained=True/False)`


## Motivation

code like this can be simplified
https://github.com/huggingface/transformers/blob/4469010c1be3a94f74d6448497051468f617baf2/examples/pytorch/question-answering/run_qa_no_trainer.py#L357-L365

## Your contribution

I can help to add this, if people think this is useful.
What should the argument name be? `load_weights: bool = True`?
It's just `AutoModel.from_config(AutoConfig.from_pretrained("model_name))` no?<|||||>Yes. But it requires if-else, and I don't like that. 🙃<|||||>I personally think the API with `from_pretrained` and `from_config` is nice and quite flexible. Adding a second way of doing the same thing looks like it would complicate things :)<|||||>That's a good point. Thank you. :)