callparticipants: replace C++ filter proxy models with QML-SFPM

src/app/calladapter.cpp

src/app/calladapter.h

src/app/callparticipantsmodel.cpp

src/app/callparticipantsmodel.h

src/app/currentconversation.h

src/app/mainview/components/CallActionBar.qml

src/app/mainview/components/ParticipantsLayer.qml

src/app/mainview/components/ParticipantsLayoutHorizontal.qml

src/app/mainview/components/ParticipantsLayoutVertical.qml