Add TryConvert for NonZero types

[ankane]

This PR adds support for NonZero types, which is part of std::num.

I tried using NonZero<T>, but ZeroablePrimitive is a nightly trait, so used a macro instead. It raises an ArgumentError if the value is zero, but I think a TypeError would work as well.

Edit: Switched to NonZeroI8, NonZeroI16, etc. since NonZero<T> is not available in 1.61.

[matsadler]

Thank you! This looks good. Could you rebase on main, that should fix the failing tests, and then I'll merge this.

[ankane]

Thanks @matsadler!