Refactor status cache and remove complex serialize/deserialize (#5335)

automerge

runtime/src/accounts_index.rs

@@ -143,7 +143,7 @@ impl<T: Clone> AccountsIndex<T> {
 
     pub fn add_root(&mut self, fork: Fork) {
         assert!(
-            (self.last_root == 0 && fork == 0) || (fork > self.last_root),
+            (self.last_root == 0 && fork == 0) || (fork >= self.last_root),
             "new roots must be increasing"
         );
         self.last_root = fork;