Fix constructor cleanup

[Adarsh-NP]

This PR adds the feature to clean local variables declared inside the initializer of a class. Please refer to tests to understand the scenarios.
Points to look into:

• In case of more than one init in a single file, this fails. While the reasoning is a bit unclear, the suspect is that piranha gets confused in the initializer scope in presence of another init because we are not able to differentiate on parameters.
• This PR doesn't clean the variable declarations inside computed variables which is a regression compared to earlier versions. This is happening because we've restricted delete_field_intialization to only clean variables declared with modifiers which was cleaning these cases as well earlier. It doesn't anymore because we are restricting to have a visibility modifier.