[NORMATIVE] Limit valid frame distance for mfmv projection
[NORMATIVE] Limit valid frame distance for mfmv projection

Set the maximum frame distance to be 32. If a reference motion
vector needs to span across two frames at distance more than 32,
drop the use of this reference motion vector.

BUG=aomedia:1394

This also clears ubsan warnings in unit tests.

Change-Id: I98b72b5fd2a885661542bbc5f8da1886d77f889f

GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom