[FR] Improve Handling and Representation of Empty Block/Item/Text Display Nodes

[Dearliet]

• Remove the message No elements defined for <block/item> model 'minecraft:<block/item>/air when minecraft:air is used, as it may give users the impression of an error.
• Represent empty block/item display nodes as a 16x16x16 wireframe (for a scale of 1x1x1) that can be manipulated (positioned, rotated, scaled).
• Address the visual differences between "" and {"text":""} for empty text display nodes in the editor.
• Determine how empty text display nodes should be visually represented