Emit respective changed signals when audio and video settings get resolved during recording

When we start recording with QMediaRecorder, the backend resolves the encoder settings. If the backend does not support the specified encoder settings it will resolve them to supported ones and emits encoderSettingsChanged(). This should be changed to the specific signals: 

encodingModeChanged();
qualityChanged();
videoResolutionChanged();
videoFrameRateChanged();
videoBitRateChanged();
audioBitRateChanged();
audioChannelCountChanged();
audioSampleRateChanged();
 
Also, we should make sure that the changed settings are correctly reported from all backends.