["shade": false] is ignored by item frames

Reported separately from MC-248703 as the item frame is its own thing, unlike the cases in that ticket which involve existing block models being used in other circumstances.

The bug

Unlike other models, item frames completely ignore the "shade" parameter which can be specified in block models. This is likely due to them being an entity rather than a proper block, but this is an issue nonetheless.

How to reproduce

Attached to this ticket is a resource pack which replaces the item frame model with a model composed of intersecting white planes. With shade disabled in the model, it should appear solid white. Were it not disabled (or, in the case of the ticket, if the game just disregards it), the planes would be shaded differently depending on direction, and their intersections would highlight the different color regions. Indeed, this is what happens for item frames. The resource pack also replaces the stone button model with this model, which highlights how the item frames should look.

1. Download and apply the resource pack

2. Place an item frame

3. Place a stone button for comparison

Expected results

The stone button and item frame would both appear completely white.

Actual results

Only the stone button appears completely white - the item frame appears as several different shades of gray.

How to fix

Item frames should recognize and respect the "shade" parameter in models just like blocks do.