Add optional debug logs for state machine transitions
Add optional debug logs for state machine transitions

Enable logs by setting the `RTSMEDIAPLAYER_DEBUG_STATE_MACHINE` environment variable.

germc/SRGMediaPlayer-iOS,germc/SRGMediaPlayer-iOS,SRGSSR/SRGMediaPlayer-iOS,fredhdroz/SRGMediaPlayer-iOS,fredhdroz/SRGMediaPlayer-iOS