Refactor LawSource_Behaviour class

## Refactor

### Description
`LawSource_Behaviour` contains the calls to gather sources/versions and display them. These calls are placed behind a button and coded inside the `.performAction()` call. The refactor would consist of extracting the different functions from `.performAction()` function and place them in seperate methods for clarity.

Start by locating the LawSource_Behaviour class and inspecting its .performAction() method. Separate the source-gathering, version-gathering, and display calls into distinct methods while preserving the button's behavior; done means the logic is no longer embedded directly in .performAction().

Written by the indexing model from the issue text.