[feat] gva: add previous_hash dividend field

lib/dubp/block-doc/src/block.rs

lib/dubp/block-doc/src/block/v10.rs

lib/modules/gva/resources/schema.gql

lib/modules/gva/src/schema/entities/block.rs

lib/modules/gva/src/schema/queries/block.rs

lib/modules/gva/src/schema/queries/current.rs