1.21.4 - Implement `item_model` alternative to `CustomModelData`

[LoneDev6]

Minecraft 1.21.4 changes how CustomModelData is handled both in NBT and configurations, so I have to generate an overlay to support that, or completely get rid of CustomModelData and start using the new item_model component.

• https://minecraft.wiki/w/Data_component_format/item_model
• https://www.minecraft.net/en-us/article/minecraft-snapshot-24w36a (1.21.2)
• https://www.minecraft.net/zh-hans/article/minecraft-snapshot-24w45a (1.21.4)

[LoneDev6]

I implemented the overlay to support 1.21.3 some updates ago on #4237 , so this is not really a requirement but a an optional feature.