Recognize MagicYUV sample entries in the built-in go-mp4 probe and consider the
probe's codec in addition to the metadata codec when applying the FFmpeg exclude
list, so a video can be matched even when one detector misses it. Rename the
shared sample-entry scan limit to CodecHeadScanLimit.
Also exclude the Matroska Video for Windows wrapper (v_ms/vfw/fourcc) by default,
since its actual codec is not exposed by metadata and the format is uncommon.