Image animation fixes and updates

[AnonymouX47]

• Fixes and Improves image iteration.
  • Directly adjusting image seek position no longer affects iteration.
  • Improves control flow in ImageIterator._animate().
• Implements non-linear image iteration via ImageIterator.seek().
• Introduces concurrent and parallel frame rendering for TUI animations.
• Frames are now rendered ahead of the animation (when possible).
• Improves TUI animation performance.
• Introduces smooth navigation across animated images (no more waiting for the first frame to be rendered before moving on).