ReportHandler.save() method config=None case only works for MIA

# Issue
## Problem Description
In the save() method for report handler it tries to set a default config when "None" config is given.
This method is supported for MIAResult with
`AttackFactoryMIA.attack_classes[attack_name].get_default_attack_config()`

For other attacks, e.g. GIAResults where there is both InvertingConfig and HuangConfig, this is not currently supported

## Expected Behavior
ReportHandler.save() should either handle them based on resulttype (MIAResult, GIAResults, ... ) or better yet, have a more generic way of handling it.

## What Needs to be Done
Implement a default config method for GIAResults/AttackFactoryGIA

## How Can It Be Tested or Reproduced
Various attacks, including GIA should be saved preferebly with a type-specific default config implementation when config=None is given