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: https://github.com/rust-lang/portable-simd/blob/283acf44cc889a159483c4805cf29c75d6c13735/crates/core_simd/tests/ops_macros.rs#L553

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!