Add mod to U128 (#6771)

## Description

The `mod` trait implementation was missing for `U128`. This has been
added.

## Checklist

- [x] I have linked to any relevant issues.
- [x] I have commented my code, particularly in hard-to-understand
areas.
- [x] I have updated the documentation where relevant (API docs, the
reference, and the Sway book).
- [x] If my change requires substantial documentation changes, I have
[requested support from the DevRel
team](https://github.com/FuelLabs/devrel-requests/issues/new/choose)
- [x] I have added tests that prove my fix is effective or that my
feature works.
- [x] I have added (or requested a maintainer to add) the necessary
`Breaking*` or `New Feature` labels where relevant.
- [x] I have done my best to ensure that my PR adheres to [the Fuel Labs
Code Review
Standards](https://github.com/FuelLabs/rfcs/blob/master/text/code-standards/external-contributors.md).
- [x] I have requested a review from the relevant team or maintainers.

Co-authored-by: K1-R1 <[email protected]>
Co-authored-by: IGI-111 <[email protected]>

sway-lib-std/src/u128.sw

@@ -668,6 +668,17 @@ impl core::ops::Divide for U128 {
     }
 }
 
+impl core::ops::Mod for U128 {
+    fn modulo(self, other: Self) -> Self {
+        assert(other != Self::zero());
+
+        // a mod b = a - b * (a / b)
+        let quotient = self / other;
+        let product = quotient * other;
+        self - product
+    }
+}
+
 fn u64_checked_add(a: u64, b: u64) -> Option<u64> {
     let of = asm(a: a, b: b, res) {
         add res a b;

test/src/in_language_tests/test_programs/revert_inline_tests/src/main.sw

@@ -18,4 +18,4 @@ fn pass_revert_require() {
 #[test(should_revert)]
 fn revert_revert_with_log() {
     revert_with_log("error")
-}
+}