Make pc protocol entity metadata consistent across all versions

[extremeheat]

entity_metadata is now a named mapper on 1.20.5+ https://github.com/PrismarineJS/minecraft-data/blob/master/data/pc/1.20.5/proto.yml#L938

but this change needs to be applied to all the old versions also. As the enum values change across versions, this causes errors if the metadata numeric indexes are not updated correctly in user code (like in flying-squid) based on the version.