system-program: Remove zero lamport check on transfers (#17726)

* system-program: Move lamports == 0 check on transfers

* Address feedback

* Update stake split to explicitly allocate + assign

* Update stake tests referring to split instruction

* Revert whitespace

* Update split instruction index in test

* Remove unnecessary `assign_with_seed` from `split_with_seed`

* Fix stake instruction parser

* Update test to allow splitting into account with lamports

tokens/src/commands.rs

@@ -1467,7 +1467,7 @@ mod tests {
         )); // Same recipient, same lockups
     }
 
-    const SET_LOCKUP_INDEX: usize = 4;
+    const SET_LOCKUP_INDEX: usize = 5;
 
     #[test]
     fn test_set_split_stake_lockup() {