VoctoGui does not embed imagesinks on Wayland

[derpeter]

On ubuntu 20.10 the video displays in the gui appear as seperate windows instead docked in UI.
This broken for x xv gl and vaapi surfaces.

To make this more fun the glade editor shipped with 20.04 crashes on the ui file.

[danimo]

This may be an issue with Wayland being the default on Ubuntu now. Voctomix is not yet compatible with Wayland and tries to XEmbed the imagesinks, which is bound to fail.

[danimo]

At least Glade no longer crashes under Wayland in 22.04 :)

[danimo]

Here is a proposal on how to do it with glimagesink: https://gist.github.com/jonasl/92c1ef32cfd87047e15f5ae24c6b510e. This needs to replace the self.imagesink.set_window_handle(self.xid) logic in òn_syncmsg` required for XEmbed. Requires refactoring into two classes with different embed strategies, and with an interchangeable imagesink.