Support multiplication on Int32x4

[zing-ethan]

Given that it is already supported by Float32x4 and also by all major SIMD instruction sets including WASM, this seems like a no-brainer.

/// Multiplication operator.
Int32x4 operator *(Int32x4 other);

[dart-github-bot]

Summary: User requests adding Int32x4 multiplication operator, mirroring Float32x4 and common SIMD instruction set capabilities. This would improve performance.

[drxddy]

Int32x4 has no support for arithmetic. Instead, we mostly use it for logical operations such as comparison and selection, branching checkout this article

please share any use case that you're looking for, I'll be happy to implement this.