Add native offhand support for *some* items

About 46 items are data-driven enough where we can tell Bedrock these items are permitted in the offhand.

core/src/main/java/org/geysermc/geyser/registry/populator/ItemRegistryPopulator.java

@@ -38,6 +38,7 @@ import org.checkerframework.checker.nullness.qual.NonNull;
 import org.cloudburstmc.nbt.NbtMap;
 import org.cloudburstmc.nbt.NbtMapBuilder;
 import org.cloudburstmc.nbt.NbtType;
+import org.cloudburstmc.nbt.NbtUtils;
 import org.cloudburstmc.protocol.bedrock.codec.v671.Bedrock_v671;
 import org.cloudburstmc.protocol.bedrock.codec.v685.Bedrock_v685;
 import org.cloudburstmc.protocol.bedrock.data.SoundEvent;
@@ -102,6 +103,13 @@ public class ItemRegistryPopulator {
             throw new AssertionError("Unable to load Java runtime item IDs", e);
         }
 
+        NbtMap vanillaComponents;
+        try (InputStream stream = bootstrap.getResourceOrThrow("mappings/item_components.nbt")) {
+            vanillaComponents = (NbtMap) NbtUtils.createGZIPReader(stream, true, true).readTag();
+        } catch (Exception e) {
+            throw new AssertionError("Unable to load Bedrock item components", e);
+        }
+
         boolean customItemsAllowed = GeyserImpl.getInstance().getConfig().isAddNonBedrockItems();
 
         // List values here is important compared to HashSet - we need to preserve the order of what's given to us
@@ -531,6 +539,25 @@ public class ItemRegistryPopulator {
                 }
             }
 
+            for (Map.Entry<String, Object> entry : vanillaComponents.entrySet()) {
+                String id = entry.getKey();
+                ItemDefinition definition = definitions.get(id);
+                if (definition == null) {
+                    // Newer item most likely
+                    GeyserImpl.getInstance().getLogger().debug(
+                            "Skipping vanilla component " + id + " for protocol " + palette.protocolVersion()
+                    );
+                    continue;
+                }
+
+                NbtMapBuilder root = NbtMap.builder()
+                        .putString("name", id)
+                        .putInt("id", definition.getRuntimeId())
+                        .putCompound("components", (NbtMap) entry.getValue());
+
+                componentItemData.add(new ComponentItemData(id, root.build()));
+            }
+
             // Register the item forms of custom blocks
             if (BlockRegistries.CUSTOM_BLOCKS.get().length != 0) {
                 for (CustomBlockData customBlock : BlockRegistries.CUSTOM_BLOCKS.get()) {

core/src/main/resources/mappings

@@ -1 +1 @@
-Subproject commit ec45f59c8590945c9226921ef7e339f510983dc1
+Subproject commit 88e50df1008916c266428ac11f76f07dc24638c5