Refactor activation Hessian computation using model builder

[ofirgo]

Pull Request Description:

Removing the old dedicated mechanism that used inference on the model's graph to compute Hessian approximation with respect to intermediate activation tensors.
Instead, the new solution utilizes the model builder to build a model from the graph and then performs the Hessian approximation computation on the model.

Checklist before requesting a review:

• I set the appropriate labels on the pull request.
• I have added/updated the release note draft (if necessary).
• I have updated the documentation to reflect my changes (if necessary).
• All function and files are well documented.
• All function and classes have type hints.
• There is a licenses in all file.
• The function and variable names are informative.
• I have checked for code duplications.
• I have added new unittest (if necessary).