Fix Unity media stream lifetime leaks and add latest-frame video coalescing#198

xianshijing-lk wants to merge 6 commits intomainlivekit/client-sdk-unity:mainfrom

sxian/CLT-1/fix_audio_video_streams_leakslivekit/client-sdk-unity:sxian/CLT-1/fix_audio_video_streams_leaksCopy head branch name to clipboard