[naga] Allow Scalar for MathFunction::Distance

[bernhl]

Description
As per https://www.w3.org/TR/WGSL/#distance-builtin the distance function should allow float scalars.

Checklist

• Run cargo fmt.
• Run taplo format.
• Run cargo clippy --tests. If applicable, add:
  • --target wasm32-unknown-unknown
• Run cargo xtask test to run tests.
• If this contains user-facing changes, add a CHANGELOG.md entry.

[ErichDonGubler]

@bernhl: Hey! Welcome to the WGPU community, and thanks for taking the time to contribute.

CI is failing because we have actually invalidated a snapshot test; we exercise a diagnostic in wgsl_errors called too_many_arguments_2 which lists all the overloads for distance specifically. Because you added some overloads, that set has expanded, and the snapshot needs the output for them.

I pushed a fixup! commit that adds these overloads. I'll squash the commit into yours once CI has passed, at which point we'll merge into trunk.

[ErichDonGubler]

Just added a CHANGELOG entry for this, too, since this is a nice user-facing change. 🙂

[jimblandy]

Thanks!