Basic check of media recorder functionality

We should be able to check the minimal functionality of media recording upon RTA testing. For auto and manual testing, you may use the example multimedia/video/recorder that can record video from cameras, screens, application windows, and audio.

Note, that it is important to check that the FFmpeg plugin is in use, see https://bugreports.qt.io/browse/QTQAINFRA-6487

For auto testing, the first step that's nice to implement:

• run a recording with default settings and any video source. Note, on macOS screen capture permissions have to be granted to the application.
• stop the recording
• make sure the media appears in the captures list in the example application.
• run the recorded media and check that the app has not crashed, and maybe that the video is finished in some time if it's possible to check with Squish.