[naga] Fix issues with const evaluation of bitwise shifts

[andyleiserson]

Fixes two issues with const evaluation of bitwise shifts:

• Disallows mixed scalar/vector shifts (scalar << vector or vector << scalar), which should not be allowed.
• Detects overflowing runtime << constant shifts at constant evaluation time.

Also includes, as a separate commit, cleanup of some noisy log messages in the naga expression validator.

Testing
Enables CTS tests.

Squash or Rebase? Rebase

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.

[teoxoy]

Looks like CI is unhappy.

[andyleiserson]

The previous version was pretty broken (in that it would not raise the error in the cases it intended to) because the constant evaluator is only capable of resolving the type of constant expressions.

So I had to move the check to the validator. I also fixed handling of 64-bit shift operands and added some tests in wgsl_errors.

The substantive changes from the previous version are limited to the last commit.

[teoxoy]

I think doing this here is unexpected. If we need this abstracted, adding a separate function that does this would be better.

[andyleiserson]

Yeah, probably so. I removed it... when it comes at the overhead of an extra function call, it doesn't really feel like it's worth the characters it saves over writing fn foo() { } in each test case.