Returns the memory representation of this integer as a byte array in
big-endian (network) byte order.
# Examples
Basic usage:
```
# use ::exint::primitive::*;
# ::exint::uint! {
use exint::Saturating;
assert_eq!(Saturating(0x123456_u24).to_be_bytes(), [0x12, 0x34, 0x56]);
# }
```