Experience orb animation is hardcoded

The bug

Experience orbs are animated visually, fading from yellow to green to yellow repeatedly. However, unlike other in-game texture animation, this is entirely hardcoded.

How to reproduce

1. Inspect the texture files for experience orbs
2. Look how they render in-game

Expected results

Since experience orbs are animated, this animation would be defined like other animations are in resource packs, using the mcmeta system.

Actual results

The animation is hardcoded. There is no way to disable the animation (or create a custom animation) using resource packs.

How to fix

Experience orbs would be made to use the mcmeta system for animations, like all other looping animations in-game. This may also involve splitting experience_orb.png into eleven files, one per orb, and having one mcmeta each.