Move VV specific item handling out of component<->nbt conversion in 1.20.3->1.20.5 (#4094)

The current code backups the tag in CUSTOM_DATA inside the toStructuredItem function which in VB is used for to server packets which causes bad data, this PR moves the backup logic out to the VV specific handler and also prevents toOldItem logic for using the backup to ever get executed in VB. The counterpart PR will add proper handling for CUSTOM_DATA.

Fixes https://github.com/ViaVersion/ViaVersion/issues/4092

common/src/main/java/com/viaversion/viaversion/protocols/v1_20_3to1_20_5/rewriter/BlockItemPacketRewriter1_20_5.java

@@ -376,13 +376,15 @@ public final class BlockItemPacketRewriter1_20_5 extends ItemRewriter<Clientboun
             return StructuredItem.empty();
         }
 
-        // Add the original as custom data, to be re-used for creative clients as well
         final CompoundTag tag = item.tag();
+        final Item structuredItem = toStructuredItem(connection, item);
+
+        // Add the original as custom data, to be re-used for creative clients as well
         if (tag != null) {
             tag.putBoolean(nbtTagName(), true);
+            structuredItem.dataContainer().set(StructuredDataKey.CUSTOM_DATA, tag);
         }
 
-        final Item structuredItem = toStructuredItem(connection, item);
         // Add data components to fix issues in older protocols
         appendItemDataFixComponents(connection, structuredItem);
 
@@ -415,7 +417,8 @@ public final class BlockItemPacketRewriter1_20_5 extends ItemRewriter<Clientboun
         final StructuredData<CompoundTag> customData = data.getNonEmpty(StructuredDataKey.CUSTOM_DATA);
         final CompoundTag tag = customData != null ? customData.value() : new CompoundTag();
         final DataItem dataItem = new DataItem(item.identifier(), (byte) item.amount(), tag);
-        if (customData != null && tag.remove(nbtTagName()) != null) {
+        if (!dataConverter.backupInconvertibleData() && customData != null && tag.remove(nbtTagName()) != null) {
+            // Skip for VB since it's used for incoming item data
             return dataItem;
         }
 
@@ -605,8 +608,6 @@ public final class BlockItemPacketRewriter1_20_5 extends ItemRewriter<Clientboun
             // Restore original data components
             restoreFromBackupTag(backupTag, data);
         }
-
-        data.set(StructuredDataKey.CUSTOM_DATA, tag);
         return item;
     }