Currently the the animation players cache is hard coded to 30 frames (which is quite low).

This causes larger files that take longer to load to become unplayable as they never load into memory and there is no way of allowing them to load into memory.

This change uses the system preference to limit caching by memory instead of number of frames.

This makes it possible to for the files in T81751 to playback smoothly.

There are details that could be changed in this patch, this is a quick test to see if it's a direction worth going.

• This could be a separate preference exposed in the animation-player section of the UI, as users might not want this limit to be used twice (possibly using double the intended memory).

• In the test files in T81751, frame skipping prevents images from being loaded into cache, causing multiple loops to be played before all images load and playback is smooth.
  
  Frame skipping could be disabled as long as cache is being filled, although I think this is outside the scope of this patch.

We could put these kinds of changes on-hold as the entire system could use bigger improvements, threaded image loading for e.g, although even in this case the ability to keep more images in cache seems reasonable.