spx: Animation binding

[nighca]

• Support "default" status for animation binding

  If

  • Current sprite not in other status (die, step, etc.)
  • Current sprite not playing other animations

  The animation bound to "default" status will be played automatically & repeatedly

• Support binding one animation to multiple statuses

[nighca]

And

• The animation bound to status Step & Default is expected to be played repeatedly, if the status duration is longer than the animation's duration.
• The animation bound to status Die is expected to be played only once when "dying" happened, even if the status duration is longer than the animation's duration.