refactor(kfn): Refactor KRandom implementations using declarative macro

[JimmyShi22]

This pull request refactors the implementation of the KRandom trait for integer types in random.rs to significantly reduce boilerplate and improve maintainability. Instead of writing separate implementations for each integer type, a macro is introduced to generate them automatically.

Trait implementation refactoring:

• Introduced the impl_krandom! macro to implement the KRandom trait for multiple integer types, replacing twelve separate manual implementations with a single macro invocation.
• Applied the macro to all relevant integer types: u8, u16, u32, u64, u128, usize, i8, i16, i32, i64, i128, and isize.

[cursor]

PR Summary

Low Risk
Pure refactor that centralizes duplicated trait impl code; behavioral risk is minimal aside from potential subtle size/cast mistakes across integer types.

Overview
Refactors KRandom integer implementations in kfn/random.rs by replacing 12 hand-written impl blocks with a single impl_krandom! declarative macro invocation.

The generated impls now uniformly call krandom using core::mem::size_of::<T>(), reducing boilerplate while keeping the same set of supported integer types.

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