Add abs_diff function to SimdInt and SimdUint traits

[okaneco]

Implement abs_diff for signed and unsigned integer vectors

[calebzulawski]

Thank you! Can you move the test under the macros that generate all of the int/uint tests? That will allow the function to be fuzzed over all the types/lane counts/inputs. I think you can copy another test that takes 2 inputs.

[calebzulawski]

I think it would be the same as this:

portable-simd/crates/core_simd/tests/ops_macros.rs

Line 553 in 283acf4

fn copysign<const LANES: usize>() {

However, it should be under the signed and unsigned tests, not float.

[okaneco]

Thanks, I'll give that a try

[okaneco]

Removed the original test file I added
Added the tests to impl_signed_tests and impl_unsigned_tests

With that advice, it was easy to add the tests

[calebzulawski]

Looks good, thanks!