"pack.png" is not supported for data packs, causing inconsistencies with resource packs

The bug

When attempting to use a pack.png file for a data pack, it would not load. Instead, a default Cobblestone block icon is used in place of the file just like the vanilla data pack.

This causes inconsistencies with resource packs as pack.png files are supported for them unlike data packs.

How to reproduce

1. Download the data pack below for easier reproduction.
2. Create a new world, and then click on the "Data Packs" folder.
3. Drag and drop the data pack into the game window, and then confirm.
   → You will notice that the icon did not load.