Provide support for std number wrappers

[DarkFenX]

Two wrappers which help controlling behavior of overflow are Wrapping and Saturating.

This is general request, personally I need only small part of it. Currently, I have to reimplement LCM manually:

impl Count {
    pub(crate) fn lcm_saturating(self, other: Self) -> Self {
        if self == Self::ZERO || other == Self::ZERO {
            return Self::ZERO;
        }
        let gcd = num_integer::gcd(self.0, other.0);
        match (self.0 / gcd).checked_mul(other.0) {
            Some(lcm) => Self(lcm),
            None => Self::MAX,
        }
    }
}

When instead it could've been a thin wrapper around num_integer call:

impl Count {
    pub(crate) fn lcm_saturating(self, other: Self) -> Self {
        Count(num_integer::lcm(Saturating(self.0), Saturating(other.0)).0)
    }
}

[MathieuDuponchelle]

Similar request for prev_multiple_of and next_multiple_of:

eprintln!("prev multiple: {}", i32::MIN.prev_multiple_of(&13));

thread 'lib::video::tests::test_fixate_step_range' (1589680) panicked at /home/meh/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/num-integer-0.1.47/src/lib.rs:845:1:
attempt to subtract with overflow