Blender Git Loki

PlayAnim: support limiting the cache by memory instead of frames

Partial fix for T81751 which exposes multiple playback performance
issues. Previously the cache was limited to 30 frames, without a way to
increase the cache for smooth playback with files that are slow to load.

Now the animation plays back smoothly once loaded into cache.

The cache limit from the system preference is used
when the player is launched from Blender.

A new player argument `-c <cache_limit>` was added to support this.