Spawners are transparent in Fast graphics

Closely relates to MC-249271 and may also relate to MC-29432.

The bug

Unlike leaves, spawners remain completely see-through even in Fast graphics. The rarity of spawners likely stops this from being a major issue, but it's still somewhat inconsistent.

How to reproduce

1. Place leaves
2. Place a spawner
3. Use Fast graphics

Expected results

Both the leaves and spawner would be opaque.

Actual results

The leaves are opaque, but the spawner is not.