All the list model tests were leaking items,
because g_list_model_get_item is transfer full.
Fixing these unveils a crash in the treelistmodel
and maplistmodel tests.
The code previously forgot to include the left child of the model's
node. Which of course only happened if that child wasn't NULL, which is
a common case.
Found and test provided by Matthias Clasen.
The calls used old bugzilla URLs and nobody cared about that.
So apparently they are very unused.
There's also a potential conflict between gitlab and bugzilla URLs and
what base bug to use there.
The old usages have been converted to comments.
