AutoModel.from_config() should attempt to load model relative to where the config was loaded.

### System Info Currently if you do an AutoConfig.from_pretrained() and then use that config to try to AutoModel.from_config() it loses the context from where the config.json was loaded. This wouldn't be a problem if AutoModel.from_config() also took a path_or_model_id style param but it doesn't. This becomes problematic mainly for situations where you want to write single code for both training and fine tuning models. In this workflow, the notion of training and fine tuning is largely the same code so creating the model to then train looks something like this: ``` try: model = AutoModel.form_pretrained(..., config=conf, ...) except OSError, ValueError: model = AutoModel.from_config(conf) ``` If you're loading models from file like i am, not being able to easily AutoModel.from_config() with a specified path is problematic. I would like all of my intermediate training steps to be done locally to potentially unrelated directory structures to the source. I think that we have two easy options. 1. Add a field to the PretrainedConfig which is only populated when it's loaded from file which is the path to the config file the config was loaded from. We can call it something like _loaded_from_file. It would have to be removed prior to save() 2. allow AutoModel.from_config() to take a path_or_model_id in addition to the config. so the call would look something like: ``` model = AutoModel.from_config(conf, path_or_model_id='/path/to/dir/containing/model') ``` cc: @Rocketknight1 Trying out recommended workflow of issuing bugs before PRs. ### Who can help? _No response_ ### Information - [ ] The official example scripts - [ ] My own modified scripts ### Tasks - [ ] An officially supported task in the `examples` folder (such as GLUE/SQuAD, ...) - [ ] My own task or dataset (give details below) ### Reproduction 1. Load a model config specifying custom code in the AutoMap from a path that is not also valid as `$CWD/model-id/model` 2. try to instantiate a version o…