Skyveil Cloudlands Pass 4

Added weeping-willow-style cloud trees generated from existing Skyveil cloud materials.

Design:
- Trunks use dense_cloud and soft_cloud.
- Leaf/canopy portions use thin_cloud and mist_cloud so they read as transparent/wispy cloud foliage.
- Canopies include hanging mist_cloud curtains to create a weeping-willow silhouette.
- Each cloud tree places 0 to 3 glowstone fruits/lights by default.
- Large cloud islands can generate randomized small forests.
- Smaller cloud islands generate 0 to 3 trees by default.

New command:
/skyveilcloudlands populate_trees_near <radius>

New config values:
- enable_cloudlands_cloud_trees
- cloudlands_cloud_tree_forest_min_radius
- cloudlands_cloud_tree_large_island_min
- cloudlands_cloud_tree_large_island_max
- cloudlands_cloud_tree_small_island_max
- cloudlands_cloud_tree_min_height
- cloudlands_cloud_tree_max_height
- cloudlands_cloud_tree_canopy_min_radius
- cloudlands_cloud_tree_canopy_max_radius
- cloudlands_cloud_tree_max_glowstone_fruits

No new mobs, structures, portals, or dimensions were added in this pass.
