Hi Experts:
I am happy to send out the first draft of vvc decoder.
It's not ready for upstream yet, but it's a good base ground for review and
future improvement.

It has the following features:
* C only
+ Fast. On a 4 cores laptop, it can get 30~35+ fps for 10bits 1080P.
+ Support traditional features I, P B frames, 8/10 bits, chroma 400,420,
422, and 444,
+ Support VVC new tools like MIP, CCLM, AFFINE, GPM, DMVR, PROF, BDOF,
LMCS, ALF
-  Not support RPR, PCM, IBC, PALETTE, and other minor features yet.

Please help review the attached patch and provide your valuable comment.
I also created a GitHub repo https://github.com/ffvvc/FFmpeg to
collaborate. Any improvement or issue report is welcomed.

Thank you.