Summary:
Some apps initially show their window with bogus/useless window
metadata and then update to useful metadata during early startup.
For example, LibreOffice sets WM_CLASS to soffice/Soffice and
then updates to libreoffice-writer/libreoffice. This leads to
a poor user experience on particular the Icons-only Task Manager,
but also the regular Task Manager depending on settings.

Depending on its configuration (and Icons-only Task Manager is
a particular set of configuration options, as far as the model
is concerned), TasksModel will try to sort a new window task
adjacent to its launcher task. The appearance of a new window
task also causes matching (in terms of identification) launcher
or startup tasks to be filtered out. To the user, this forms a
lifecycle of the launcher being replaced by the window in-place
(and a startup state inbetween, optionally but by default).

Prior to this patch, this sorting decision was only done once,
when...