New bed model is unoptimized and has many excess faces

Relates to MC-279350.

The third 26.2 snapshot finally makes beds controlled by the block model system again, which is a massive improvement. However, the mapping is somewhat wasteful and can contribute to a performance deficit in areas where many beds are used, such as villager breeding systems. The bed models use 15 quads each, even though the same visual result can be achieved using just 9, with less of a performance hit (and smaller file sizes) as a result.

A resource pack implementing this optimization is attached to this ticket; Mojang have my full permission, and strong encouragement, to use these assets to improve the bed model system.

To reproduce/check the improved performance:

• Create a “The Void” superflat world

• Run the following commands:

• /tick freeze
  /fill 24 -60 -8 -8 256 -8 pink_bed[part=head]
  /fill 24 -60 -7 -8 256 -7 pink_bed[part=foot]
  /fill 24 -60 -6 -8 256 -6 pink_bed[part=head]
  /fill 24 -60 -5 -8 256 -5 pink_bed[part=foot]
  /fill 24 -60 -4 -8 256 -4 pink_bed[part=head]
  /fill 24 -60 -3 -8 256 -3 pink_bed[part=foot]
  /fill 24 -60 -2 -8 256 -2 pink_bed[part=head]
  /fill 24 -60 -1 -8 256 -1 pink_bed[part=foot]
  relog

  /tp @s 8 -60 24 180 -45

• Check the frames per second you get with the resource pack applied, versus without

Expected results: good performance

Actual results: we get much better performance with the resource pack in use

How to fix: rework the bed models to use less faces while still looking the same, as the resource pack demonstrates