This ports the application to libadwaita, enabling us to use the libadwaita stylesheet and
widgets to better implement the Gnome Human Interface Guidelines.
Format params for links and ports are now being watched for in the pipewire connection code.
The parsed media type is then set on the port widget / link object
and they are colored accordingly.
For ports, which were already colored before, this new method of determining the media type
should be more reliable and accurate as this uses the real Format/EnumFormat
params instead of parsing optional properties.
The graph widgets management (watching a glib receiver, adding and removing
Nodes, Ports and Links) currently done in the `Application` and `GraphView`
objects has been extracted into a new GraphManager object, which watches the
receiver instead, pushes changes directly to the widgets, and reacts to their signals.
This seperates widget logic and management logic cleanly instead of both
being mixed into the GraphView, and also reduces the code size for the
Application object.
This is more reliable than assuming the link carries the id of its nodes, as there have been cases where a link was created without those
properties set.
Instead, we can just pull them from the state via the port ids of the link.
Glib MainContext is now aquired manually because a change in gtk-rs would lead to
a panic when attaching the receiver otherwise, because gtk::init() doesn't
"leak" the default main context anymore.
This extends the `Application` struct to keep more advanced state.
This state is then used to determine the needed information to create
or delete a link between the two connected ports.
A message to create/delete the link is then send to the pipewire thread,
which executed the request.
The `View` sturct was mostly a layer of indirection, and the controller benefitted by absorbing the gtk::Application
subclass parts, so now those two are merged into a new gtk::Application subclass.
The pipewire loop now runs without interruption in a second thread and communicates with
the GTK thread via a channel in each direction, instead of checking for events once a second and using callbacks.
This allows changes to appear instantly in the view, instead of having to wait.
struct PipewireConnection is now decoupled from any other components, another component (the controller)
can receive updates by registering a callback.
struct PipewireState has been refactored to a struct Controller.
It still keeps state and manages the view, but now also actively requests updates from the pipewire connection via callback.
