Mapping for additional input dir through extra_models_path.yaml or args

### Feature Idea

`extra_model_paths.yaml` has been pretty useful in terms of mapping models & custom nodes from two different directories.

It works for models & custom nodes, but building it in more generic way to accept include all paths such as `input`.

Here is the overall idea:

in extra_model_paths.yaml

```
other_ui:
base_path: /home/ubuntu/
input: additional_inputs
custom_nodes: additional_custom_nodes
# checkpoints: models/checkpoints
# gligen: models/gligen
```

Let me know your thoughts & if you are open for a PR.

### Existing Solutions

None, tried ` --input-directory` but it changes default to input dir to specified dir. I would like to load inputs from two different dirs, default input path & an additional input path.

### Other

_No response_