Modify the voctogui UI properly using PyGObject

At the moment, the way we're modifying voctogui's UI is by modifying its code directly with ansible.builtin.lineinfile. This is clearly the wrong approach (but it works and I was running out of time at DC24).

The proper way to make modifications to the UI would be to:

1. Patch voctogui to create a proper endpoint where we can load a custom Python script late in the initialization process.
2. Use PyGObject to modify the GTK objects properties.

The properties of these objects can be debugged and changed manually by running voctogui with GTK_DEBUG=interactive.