Limit the amount of texture scaling done per frame to reduce stutters

Scaling causes really bad stutters in some games on some hardware.

This should also reduce the impact of pathological cases like the first boss of FF Type-0 to be more bearable.

Causes some extra work but the heavy work gets spread over more frames. This probably will need some testing tuning before merge.

It should do nothing to speed if scaling is not enabled.
Should this clear TexCacheEntry::STATUS_TO_SCALE here instead?  Consider this case:

1. 20 large textures appear on a frame, each 256x256 (so 20 frames to scale all.)
2. By the 20th frame, the final texture to scale has changed.  This is less frequent than 15 frames, so does not disable scaling.
3. The status is never cleared, so it gets rescaled on frame 21.

I'm not sure, there may be other cases.  That or we should clear it up where we reset all the fields / always when !match.

-[Unknown]