Ice Caves Backport

Updated Ice Caves content to 26.4 Snapshot 6:

• Added Snow Bricks, stairs, slabs and walls, with native crafting, recipe advancements, models, textures and shovel-only drops.
• Added the new Ice Crystal ambient sounds and vanilla playback conditions.
• Added Cold Sulfur Cube behavior for native Sulfur Cubes and supported Vanilla Backport cubes; Snow Bricks now work as fast-sliding food.
• Packed Ice Brick blocks now require a pickaxe for drops.
• Fixed brittle ice interactions with Strays, Shulkers, mobGriefing, spawn protection, lily pads and mob spawning.
• Zombie villagers in Ice Caves now use their snowy appearance.
• Freezing now counts toward A Furious Cocktail and How Did We Get Here, and no longer repeatedly spams the fire-extinguish sound.
• Fixed missing Ice Ball shatter bursts on Forge 1.20.1 by sending self-contained particle packets, including very short-range impacts.

Retains the earlier terrain, compatibility, icicle, ice-sound and Ice Ball particle fixes.

World-generation additions appear in newly generated chunks. Back up existing worlds before updating.