Add ConstLowerBounded/ConstUpperBounded/ConstBounded traits, impls, and tests

[linclelinkpart5]

Adds functionality as requested in #252.

This is done by adding ConstLowerBounded and ConstUpperBounded traits, with associated costs of const MIN: Self and const MAX: Self, respectively. In addition, I also included ConstBounded as a supertrait, and impl'd it for all types that implement ConstLowerBounded + ConstUpperBounded:

pub trait ConstBounded: ConstLowerBounded + ConstUpperBounded {}

impl<T: ConstLowerBounded + ConstUpperBounded> ConstBounded for T {}

These traits have been implemented for all primitive types that the existing Bounded traits have been impl'd for.

[apps4uco]

Hope you don't mind a nitpicking suggestion, the macro can be simplified:

macro_rules! const_bounded_impl {
    ($t:ty) => {
        impl ConstLowerBounded for $t {
            const MIN: Self = Self::MIN;
        }

        impl ConstUpperBounded for $t {
            const MAX: Self = Self::MAX;
        }
    };
}

const_bounded_impl!(usize);
const_bounded_impl!(u8);
const_bounded_impl!(u16);
const_bounded_impl!(u32);
const_bounded_impl!(u64);
const_bounded_impl!(u128);

const_bounded_impl!(isize);
const_bounded_impl!(i8);
const_bounded_impl!(i16);
const_bounded_impl!(i32);
const_bounded_impl!(i64);
const_bounded_impl!(i128);

const_bounded_impl!(f32);
const_bounded_impl!(f64);