Use minimal prebuilt FFmpeg for Windows

On the scrcpy-deps repo, I built FFmpeg 5.1.2 binaries for Windows with
only the features used by scrcpy.

For comparison, here are the sizes of the dll for FFmpeg 5.1.2:
 - before: 89M
 - after: 4.7M

It also allows to upgrade the old FFmpeg version (4.3.1) used for win32.

Refs <https://github.com/rom1v/scrcpy-deps>
Refs <https://github.com/Genymobile/scrcpy/issues/1753>