Should shift int/uint tests around to avoid code repetition

[pnkfelix]

Currently within

macro_rules! uint_module { ($T:ty) => (

we have, after things that do use $T, the pair of tests:

#[test]
fn test_uint_to_str_overflow() { ... }
 #[test]
fn test_uint_from_str_overflow() { ... }

that do not reference $T.

As far as I can tell, these tests do not need to be inside the macro definition. They should live outside it, so that we will not generate code for them and redundantly run them once for every integer type variant.

[alexcrichton]

Fixed in #22658