Reduce VFX additions for ring debt, flickering hud elements and cup select

This branch adds several changes to cv_reducevfx to help further reduce the amount of potentially problematic effects. These changes are a direct result of observing a photo-sensitive friend play the game, and aim to address several problem areas they experienced and which I can reasonably extrapolate would present problems if encountered. The below changes are now active if cv_reducevfx is on:

• Ring debt warning animation is swapped out for an alternate version that uses frames A and E of the existing animation to create a slow pulsing effect, removing the rapid shaking present in the standard animation. (This requires the use of an alternate state and sprite slot to display the altered animation.)
• Flickering hud elements (i.e. spraycan auras, Super Flicky) are instead simply transparent.
• Emeralds on the cup select screen have their flashing disabled. (Currently, this only goes into effect when the menu is first loaded, whether on initial game start or on returning to the menu from gameplay. I think this should be fine, given that anyone in need of reducevfx is likely to have it enabled before ever getting an emerald in the first place due to other, more intense flashing effects.)

For the ring debt replacement graphics to work, this file will need to be loaded: RingStingHardcode.pk3

(There are some leftover, unused alternatives for the spraycan aura graphics that I experimented with in the file, but they should not affect anything and will not replace the standard graphics.)

Video demonstrations of the above changes in action: ringracers0051 ringracers0055 ringracers0057