Overflow behaviour relies on Optimization about sway HOT 1 CLOSED

Easy repro without dependence on #5385

script;

fn main() {

}

fn add(a: u8, b: u8) -> u8 {
   a + b
}

#[test]
fn should_overflow_revert() {
   let a: u8 = u8::max();
   let b: u8 = 1;
   add(a, b);
}

On master, forc test hits a revert, as it should, but with mem2reg (by adding Return Ok(false) at the beginning of promote_to_registers), forc test just passes (but it shouldn't have).

from sway.