Optimize some of vanilla's block models

[muzikbike]

Request Description

Several blocks in vanilla use models that are very unoptimized, using far more texture planes than are strictly needed to achieve said appearance. We can get a visually identical result using less planes - the recent fix for issues like #1316 should eliminate any subpixel discrepancies that would otherwise exist in vanilla.

However, I'm not sure if including these optimized models in Sodium would jeopardise their implementation into vanilla for licensing reasons.

Affected models:

• Stairs (https://bugs.mojang.com/browse/MC-262461)
• Cauldrons (https://bugs.mojang.com/browse/MC-262470)
• Item frames (https://bugs.mojang.com/browse/MC-262527)
• Chorus flowers (https://bugs.mojang.com/browse/MC-262641)
• Hanging mangrove propagules (https://bugs.mojang.com/browse/MC-262689)
• Composters (https://bugs.mojang.com/browse/MC-267127)

The following fixes would also change texture mapping, which may be undesirable (even if vanilla's is wrong):

• Dragon egg (https://bugs.mojang.com/browse/MC-262652)
• Fence gates (https://bugs.mojang.com/browse/MC-262953)
• Fences (https://bugs.mojang.com/browse/MC-267281)
• Glass panes (https://bugs.mojang.com/browse/MC-267315)

Hoppers (https://bugs.mojang.com/browse/MC-262452) would require unused pixels to be removed from the top texture (https://bugs.mojang.com/browse/MC-262454). In addition, optimizing flower pots may require redoing how the texture works entirely, which might be bad news for mods that add their own potted objects based on the vanilla model (https://bugs.mojang.com/browse/MC-262427).