Function run_loop 

pub fn run_loop(
    execution: Execution,
    gas_left: &mut i64,
    handler: impl FnMut(&mut Execution, &[u8], u64, u64, u64, u64, u64, u64) -> Result<u64, ()>,
) -> RunResult

Drives the prepare/run loop calling handler for each syscall.

The closure receives (execution, syscall_symbol, a0, a1, a2, a3, a4, a5) and returns Ok(return_value) to resume or Err(()) to signal exit (trap).