Calculates the quotient of `self` and `rhs`, rounding the result towards negative infinity.
# Panics
This function will panic if `rhs` is zero or if `self` is `Self::MIN` and `rhs`
is -1. This behavior is not affected by the `overflow-checks` flag.
# Examples
Basic usage:
```
# use ::exint::primitive::*;
# ::exint::uint! {
let a = 8_i24;
let b = 3_i24;
assert_eq!(a.div_floor(b), 2_i24);
assert_eq!(a.div_floor(-b), -3_i24);
assert_eq!((-a).div_floor(b), -3_i24);
assert_eq!((-a).div_floor(-b), 2_i24);
# }
```