Use FFmpeg binaries V4.4.1. Add FFmpegScreenSource class

[ChristopheI]

In this PR:

• Bump FFmpeg.AutoGen dependency to 4.4.1.1
• Update FFmpeg binaries to 4.4.1 (cf. https://www.gyan.dev/ffmpeg/builds/#release-builds)
• Modify code to support FFmpeg lib in version 4.4.1
• FFmpegFileSource supports also URI: (for example https://upload.wikimedia.org/wikipedia/commons/3/36/Cosmos_Laundromat_-_First_Cycle_-_Official_Blender_Foundation_release.webm)
• Add FFmpegScreenSource class: Allow to share the specify part of the screen
• Enhance FFmpegFileAndDevicesTest

Tested only in Win10