Function resize_used_bits

hail-fuzz/src/load_resizer.rs:464–483

Removes upper bits from `a` and `b` for operations with partial constants. Handles cases like: ```pcode value:4 = load(value_addr) mask:1 = load(mask_addr); mask_zxt:4 = zext(mask); output = value & mask_zxt; ```

(op: pcode::Op, a: &'a [Bit], b: &'b [Bit])

///     output = value & mask_zxt;
/// ```
fn resize_used_bits<'a, 'b>(op: pcode::Op, a: &'a [Bit], b: &'b [Bit]) -> (&'a [Bit], &'b [Bit]) {
    /// We didn't support this in the original implementation, so this flag can be set to enable
    /// compatability with old traces.
    const SKIP_AND_USAGE_ADJUSTMENT: bool = false;
    if SKIP_AND_USAGE_ADJUSTMENT {
        return (a, b);
    }

    match op {
        pcode::Op::IntAnd => {
            let a_zeros = a.known_leading_zeros();
            let b_zeros = b.known_leading_zeros();
            (&a[..a.len() - b_zeros], &b[..b.len() - a_zeros])
        }

        // TODO: add additional operations (e.g., IntOr with upper ones, Bool* operations, shift
        // operations).
        _ => (a, b),
    }
}

impl icicle_vm::CodeInjector for LoadResizeInjector {
    fn inject(&mut self, cpu: &mut Cpu, group: &BlockGroup, code: &mut BlockTable) {