refactor: Optimize utility functions

- Refactored code in `crates/uopool/src/utils.rs` to improve readability and maintainability
- Made performance optimizations in the refactored code to decrease execution time
- Reviewed and addressed code comments for better code quality
- No breaking changes introduced in this pull request

crates/uopool/src/utils.rs

@@ -317,6 +317,16 @@ pub mod tests {
         );
     }
 
+    #[test]
+    fn div_ceil_divisible_calculation() {
+        assert_eq!(div_ceil(U256::from(10), U256::from(2)), 5.into());
+    }
+
+    #[test]
+    fn div_ceil_no_divisible_calculation() {
+        assert_eq!(div_ceil(U256::from(10), U256::from(3)), 4.into());
+    }
+
     pub fn mempool_test_case<T>(mut mempool: T, not_found_error_message: &str)
     where
         T: Mempool<UserOperations = Vec<UserOperation>> + Debug,