Calculates the smallest value greater than or equal to `self` that is a multiple of `rhs`.
# Panics
This function will panic if `rhs` is zero.
## Overflow behavior
On overflow, this function will panic if overflow checks are enabled (default in
debug mode) and wrap if overflow checks are disabled (default in release mode).
# Examples
Basic usage:
```
# use ::exint::primitive::*;
# ::exint::uint! {
assert_eq!(16_u24.next_multiple_of(8_u24), 16_u24);
assert_eq!(23_u24.next_multiple_of(8_u24), 24_u24);
# }
```