GStreamer 1.22 merged the videoscale plugin into the videoconvertscale
plugin. So we should check if the Element is still loadable instead of
checking the plugin name.
fixes#1352
* Initial commit for VoIP v1 implementation
* Added draft of event handlers for voip methods
* Added event handlers for VoIP events, added rejectCall, added version tracking for call version for V0 and V1 compatibility
* Added call events to the general message pipeline. Modified Call Reject mechanism
* Added message delegates for new events. Modified hidden events. Updated handle events.
* Updated implementation to keep track of calls on other devices
* Fixed linting
* Fixed code warnings
* Fixed minor bugs
* fixed ci
* Added acceptNegotiation method definition when missing gstreamer
* Fixed warnings
* Fixed linting
