Boot the Builder pattern from GenesisBlock (#6364)

genesis/src/lib.rs

@@ -1,7 +1,8 @@
 use serde::{Deserialize, Serialize};
 
+/// An account where the data is encoded as a Base64 string.
 #[derive(Serialize, Deserialize, Debug)]
-pub struct PrimordialAccountDetails {
+pub struct Base64Account {
     pub balance: u64,
     pub owner: String,
     pub data: String,