error messages returned by Ffmpeg/Fprobe are always swallowed

[boqapt]

Reproducing:

• corrupt sample video file HudlFfmpeg\Samples\Assets\sample-video.mp4 by inserting couple of spaces at the beggining of it in text editor
• start (in Visual Studio) Samples app and select [2] - ConcatVideo

Observed:
Exception is thrown with message in innermost exception "FFmpeg failed processing with an exit code of 1"

Expected:
Exception with message "Invalid data found when processing input"

Reason:
<...>.ProcessIt methods running ffmpeg/fprobe redirect only stdout, they don't redirect stderr at all but Ffmpeg prints errors (and even not errors, but statistics, header etc. - everything) into stderr

Advice how clean error message without any junk can be retrieved:
Run ffmpeg.exe with args -loglevel error -hide_banner -nostats