Show custom icons in autocompletion suggestions

[hakro]

Fixes #91721

[akien-mga]

Makes sense to me.

But might be worth evaluating what's the cost of this function in e.g. a project with a lot of class icons. I remember we wanted to do some caching, was it implemented in the end @KoBeWi ?

[KoBeWi]

get_class_icon() does not have cache, only get_script_icon() in EditorData does.
We're missing a method that uses cache and would return an icon for anything 🤔

[akien-mga]

BTW something to look into potentially:

Ref<Texture2D> ReplicationEditor::_get_class_icon(const Node *p_node) {
        if (!p_node || !has_theme_icon(p_node->get_class(), EditorStringName(EditorIcons))) {
                return get_theme_icon(SNAME("ImportFail"), EditorStringName(EditorIcons));
        }
        return get_theme_icon(p_node->get_class(), EditorStringName(EditorIcons));
}

We seem to use get_class_icon a lot already throughout the editor, so I guess one more use case shouldn't have dramatic impact if the rest of the editor behaves.

[akien-mga]

Thanks!