[P2] Support argument name based intervention

[frankaging]

Description:
When using the hook, we can now support kwargs-based inputs by reading the input as a dictionary. However, we will always assume the dictionary only contains a single input (e.g., hidden representations). This assumption can easily go wrong. What should we do instead is to specify which part of the inputs we do interventions on in the config for the model.

Note that this will still result in coupled code with the Transformers library. Multiple PRs are required to move towards this direction.