Rework excavation bonus drops

[MilesBHuff]

It has long been consensus that many (most?) of the bonus drops for excavation are quite annoying. As well, some drops trivialize the collection of materials whose collection would otherwise be kinda involved: glowstone dust and cocoa beans. And the diamond-in-the-rough odds might be slightly too high.

Proposal:

• Gravel has a chance to drop what gravel already has a chance to drop. This changes nothing significant about the game, but increases the yield of flint, bones, gunpowder, etc from gravel at higher excavation levels, which is handy given how these can be somewhat rare resources.
• Grass blocks have a chance to drop things that could conceivably be growing in that block without you immediately knowing, such as wheat seeds, carrots, potatoes, beetroot seeds, brown mushrooms, red mushrooms, grass, sticks, and whatever sapling(s) are native to the present biome.
• Podzol has a chance of dropping brown mushrooms, red mushrooms, sticks, and spruce tree saplings.
• Mycelium has a chance of dropping brown mushrooms or red mushrooms.
• Dirt blocks have a small chance of dropping coal and a miniscule chance of dropping a pottery shard. They do not drop things that could only conceivably drop from something at the surface, because unlike grass, podzol, and mycellium, dirt is not a surface-only block.
• Coarse dirt blocks have the same drops as dirt blocks, but with an added small chance of getting an iron nugget.
• Rooted dirt blocks have the same drops as dirt blocks, but with an added relatively high chance of getting sticks.
• Sand in an ocean, beach, or river biome has a miniscule chance of dropping a nautilus shell.
• Mud blocks have a chance of dropping sticks, brown mushrooms, and red mushrooms; and a small chance of dropping an iron nugget (bog iron).
• Muddy mangrove roots have the same drops as mud, but with an even higher chance of dropping sticks.
• Soul sand and soul soil have a chance of dropping bones and bonemeal, a small chance of dropping glowstone dust, a tiny chance of dropping gold nuggets, and a miniscule chance of dropping wither skulls.
• Suspicious gravel/sand are the same as their normal counterparts, but with a tiny chance of dropping a pottery shard.
• Red sand has a tiny chance of dropping a gold nugget and a miniscule chance of dropping a pottery shard.
• Farmland, concrete powder, and dirt paths drop nothing special.
• All excavatable blocks have a miniscule chance of dropping a skill CD.