* Add support for VobSub subtitle streams
* update logic to determine separate extraction for VobSub subtitles
* simplify VobSub extraction logic and fix ffmpeg command
* Match `ExtractAllExtractableSubtitlesMKS` with `ExtractAllExtractableSubtitlesInternal` Matroska's VobSub option
* Add a comments clarify why MKS was used, and remove the redundant VobSub extension branch
* remove redundant VobSub format check
* fix type errors