this commit provides a central place where all block data can go to be upgraded to the latest version (currently 1.19), irrespective of how old it is.
Previously I had issues during debugging, because it wasn't possible to just upgrade a block without deserializing it into a Block object, which isn't currently supported for many blocks.
This commit solves that problem by separating the upgrading from the deserialization.
1533fcf8f6