Draft: Update to new KPipeWire API, handle the "Rendering" state from KPipeWire
This updates Spectacle to the changes made in KPipeWire in plasma/kpipewire!173 and also handles the "rendering" state, which is used to indicate the stream is deactivating but still flushing buffers.
Draft because this somehow causes consecutive screen recordings to break and basically "fall behind" one recording.