port-filtering: extend the existing MVP

[DecFox]

We want to build upon the current implementation of the portfiltering experiment before we can deploy the testhelper (underlying issue here: #2005). Some of the proposed changes can be found here: ooni/probe-cli#891 (comment). This issue documents further functionalities in order to have a more complete experiment.

• Add a functionality to distinguish between port and IP blocking
• Add the ability to pass a ports list as input

This can be closed once we have added all the features required for a deployment and a decisive experiment.