This moves all code comprehension-related code to a new library,
LibCodeComprehension.
This also moves some types related to code comprehension tasks (such as
autocomplete, find declaration) out of LibGUI and into
LibCodeComprehension.
The ToDoEntries and ToDoEntriesWidget classes now have methods for
clearing the entries, before entries would stay permanently, even after
switching to a new project.
Most of the models were just calling did_update anyway, which is
pointless since it can be unified to the base Model class. Instead, code
calling update() will now call invalidate(), which functions identically
and is more obvious in what it does.
Additionally, a default implementation is provided, which removes the
need to add empty implementations of update() for each model subclass.
Co-Authored-By: Ali Mohammad Pur <ali.mpfard@gmail.com>
