[naga] Disallow logical operators && and || on vectors

[andyleiserson]

Connections
Fixes #6856

Description
This change disallows the logical operators && and || on vectors, which WGSL does not allow. There are two relevant codepaths, one for constant evaluation and one for type checking of expressions to be evaluated at runtime.

I tested this change locally in combination with #7339. The two changes actually do not conflict and interact minimally. In #7339, I implemented a transformation while lowering to IR that gets applied only if the operands have a correct (scalar) type. If the operands are not scalars, the expression is passed through with the expectation that validation rejects it. This change affects what will ultimately pass validation.

Arguably, these operators should be removed from the Naga IR entirely. I have not done that, because the BinaryOperator enum is shared by the AST and IR representations.

Testing
Added tests in wgsl_errors to verify both operators are rejected in both const and runtime contexts.

Squash or Rebase? Squash

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.
• Add a CHANGELOG.md entry.