Naga wgsl-in allows for mixing '+' and '^' without parenthesis, dawn doesn't

[expenses]

Similar to #6856.

I got this error in Chromium with a shader that works fine in desktop wgpu:

Compilation log for [Invalid ShaderModule (unlabeled)]:
6 error(s) generated while compiling the shader:
:67:54 error: mixing '+' and '^' requires parenthesis
        var _S4 : u32 = _S3 + (((((_S2 << (u32(4)))) + u32(2738958700) ^ (_S2 + sum_1)) ^ (((_S2 >> (u32(5)))) + u32(3355524772))));

This issue is originally caused by slang generating invalid wgpu shaders, but naga doesn't catch it.

[expenses]

Curiously, it seems like the original code did use parenthesis:

https://github.com/NVIDIAGameWorks/Falcor/blob/9dc819c162b2070335c65060436041690b7937f8/Source/Falcor/Utils/Math/HashUtils.slang#L62-L74

[sagudev]

Indeed, per spec https://www.w3.org/TR/WGSL/#operator-precedence-associativity + and ^ are in different associativity groups, hence one needs parenthesis.

[teoxoy]

Related: #4536