WritableAccount.add/subtract_lamports (#16750)

* add/sub lamports

* make add/sub return Result

* sample replacements

* cleanup

* fix up a few tests as examples

* move enum, cleanup, impl from

* fmt

* cleanup

* add lamports.rs

runtime/src/accounts_db.rs

@@ -6194,7 +6194,7 @@ pub mod tests {
             if let Some((mut account, _)) =
                 accounts.load_without_fixed_root(&ancestors, &pubkeys[idx])
             {
-                account.lamports += 1;
+                account.checked_add_lamports(1).unwrap();
                 accounts.store_uncached(slot, &[(&pubkeys[idx], &account)]);
                 if account.lamports == 0 {
                     let ancestors = vec![(slot, 0)].into_iter().collect();