Remove Bounded requirement from RealField

[boomshroom]

While most types would have minimum and maximum values, arbitrary precision types can be useful to drop into an existing function when they're needed. Obviously, arbitrary precision types lack defined minimum and maximum values preventing them from implementing RealField, and since ComplexField also requires declaring the wrapped RealField, ComplexField isn't implementable either even though it doesn't directly depend on Bounded.

The rug crate has had to close multiple issues requesting the implementation of Float from num-traits for exactly this reason.

[sebcrozet]

That make sense. Let’s remove the Bounded requirement. And let’s add two new methods to RealField that would replace that Bounded requirement:

fn max_value() -> Option<Self>;
fn min_value() -> Option<Self>;